Elsevier has created a COVID-19 resource centre with free information in English and Mandarin on ... more Elsevier has created a COVID-19 resource centre with free information in English and Mandarin on the novel coronavirus COVID-19. The COVID-19 resource centre is hosted on Elsevier Connect, the company's public news and information website. Elsevier hereby grants permission to make all its COVID-19-related research that is available on the COVID-19 resource centre-including this research content-immediately available in PubMed Central and other publicly funded repositories, such as the WHO COVID database with rights for unrestricted research re-use and analyses in any form or by any means with acknowledgement of the original source. These permissions are granted for free by Elsevier for as long as the COVID-19 resource centre remains active.
This article has been peer-reviewed and accepted for publication, but has yet to undergo copyedit... more This article has been peer-reviewed and accepted for publication, but has yet to undergo copyediting and proof correction. The final published version may differ from this proof. Human Gene Therapy Clinical Development and Commercialization of Advanced Therapy Medicinal Products (ATMPs) in the EU: how are the product pipeline and regulatory framework evolving?
Growing interest in extracellular vesicles (EVs, including exosomes and microvesicles) as therape... more Growing interest in extracellular vesicles (EVs, including exosomes and microvesicles) as therapeutic entities, particularly in stem cell-related approaches, has underlined the need for standardization and coordination of development efforts. Members of the International Society for Extracellular Vesicles and the Society for Clinical Research and Translation of Extracellular Vesicles Singapore convened a Workshop on this topic to discuss the opportunities and challenges associated with development of EV-based therapeutics at the preclinical and clinical levels. This review outlines topic-specific action items that, if addressed, will enhance the development of best-practice models for EV therapies. Stem Cells Translational Medicine 2017.
Extracellular vesicles (EVs), such as exosomes and microvesicles, are released by different cell ... more Extracellular vesicles (EVs), such as exosomes and microvesicles, are released by different cell types and participate in physiological and pathophysiological processes. EVs mediate intercellular communication as cell-derived extracellular signalling organelles that transmit specific information from their cell of origin to their target cells. As a result of these properties, EVs of defined cell types may serve as novel tools for various therapeutic approaches, including (a) anti-tumour therapy, (b) pathogen vaccination, (c) immune-modulatory and regenerative therapies and (d) drug delivery. The translation of EVs into clinical therapies requires the categorization of EV-based therapeutics in compliance with existing regulatory frameworks. As the classification defines subsequent requirements for manufacturing, quality control and clinical investigation, it is of major importance to define whether EVs are considered the active drug components or primarily serve as drug delivery vehi...
The management of clinical trial applications by public authorities is a complex process involvin... more The management of clinical trial applications by public authorities is a complex process involving several regulations, actors, and IT systems. In this paper we present a modeling approach based on semantic information models that supports this process. In particular, the approach can be used for the generation of user-centric visualizations, performance and compliance analyses and the distribution of the contained knowledge within an organization and to third parties. The approach has been developed together with AGES PharmMed and applied to their core processes.
Semantic Technologies for Business and Information Systems Engineering
The use of semantic technologies in practical scenarios requires carefully balancing the tradeoff... more The use of semantic technologies in practical scenarios requires carefully balancing the tradeoff between costs and benefits in order to gain acceptance. In this chapter we report on a project conducted together with the Austrian competent authority in regard to safety in healthcare. It is described how semantic technologies can be combined with conceptual models to support management executives in the distribution of knowledge and the analysis of compliance. The approach is based on a step-wise semantic enrichment of conceptual models with formal semantic schemata in order to support human analyses. It has been implemented on the ADONIS meta modeling platform and applied to a scenario dealing with the management of applications for clinical trials.
Advances in Experimental Medicine and Biology, 2015
With the release of Regulation 1394/2007, a new framework for gene and cell therapy medicinal pro... more With the release of Regulation 1394/2007, a new framework for gene and cell therapy medicinal products and tissue-engineered products was established in the European Union. For all three product classes, called advanced therapy medicinal products, a centralised marketing authorisation became mandatory. The European Medicines Agency (EMA) together with its Committee for Advanced Therapies, Committee for Human Medicinal Products and the network of national agencies is responsible for scientific evaluation of the marketing authorisation applications. For a new application, data and information relating to manufacturing processes and quality control of the active substance and the final product have to be submitted for evaluation together with data from non-clinical and clinical safety and efficacy studies. Technical requirements for ATMPs are defined in the legislation, and guidance for different products is available through several EMA/CAT guidelines. Due to the diversity of ATMPs, a tailored approach for regulating these products is considered necessary. Thus, a risk-based approach has been introduced for ATMPs allowing flexibility for the regulatory requirements. Since the regulatory framework for ATMPs was established, five products have been licenced in the European Union. However, the pipeline of new ATMPs is much bigger, as seen from the significant numbers of different products discussed by the CAT in scientific advice and classification procedures. In 2013, a public consultation on the ATMP Regulation was conducted by the European Commission, and the results were published in 2014. The report proposes several improvements for the current framework and established procedures for the regulation of ATMPs.
In this paper we describe a modeling method for supporting performance management by building upo... more In this paper we describe a modeling method for supporting performance management by building upon the current challenges of public health authorities. Through focusing on the performance management requirements of national competent authorities (NCA) that fulfill several duties in regard to the marketing authorization of medicinal products, we derive a modeling language, an according modeling procedure and mechanisms and algorithms. Thereby, particular requirements in regard to the compliance to legal regulations, the competition of NCAs within the European Union, the allocation of resources under uncertainty, and the specific human resource requirements of NCAs have to be taken into account. The modeling language is formally described using a meta model based approach and implemented on a meta modeling platform. For the evaluation, the modeling method has been applied in a scientific study with the Austrian national competent authority AGES PharmMed.
On September 11, 2014, a workshop entitled ‘Advanced Therapy Medicinal Products: How to Bring Cel... more On September 11, 2014, a workshop entitled ‘Advanced Therapy Medicinal Products: How to Bring Cell-Based Medicinal Product Successfully to the Market' was held at the 47th annual meeting of the German Society for Transfusion Medicine and Immunohematology (DGTI), co-organised by the European Medicines Agency (EMA) and the DGTI in collaboration with the German Stem Cell Network (GSCN). The workshop brought together over 160 participants from academia, hospitals, small- or medium-sized enterprise developers and regulators. At the workshop, speakers from EMA, the Committee for Advanced Therapies (CAT), industry and academia addressed the regulatory aspects of development and authorisation of advanced therapy medicinal products (ATMPs), classification of ATMPs and considerations on cell-based therapies for cardiac repair. The open forum discussion session allowed for a direct interaction between ATMP developers and the speakers from EMA and CAT.
Phosphoinositide-specific phospholipase C-gamma1 (PLC-gamma1) is a key enzyme that governs cellul... more Phosphoinositide-specific phospholipase C-gamma1 (PLC-gamma1) is a key enzyme that governs cellular functions such as gene transcription, secretion, proliferation, motility, and development. Here, we show that PLC-gamma1 is regulated via a novel autoinhibitory mechanism involving its carboxy-terminal Src homology (SH2C) domain. Mutation of the SH2C domain tyrosine binding site led to constitutive PLC-gamma1 activation. The amino-terminal split pleckstrin homology (sPHN) domain was found to regulate the accessibility of the SH2C domain. PLC-gamma1 constructs with mutations in tyrosine 509 and phenylalanine 510 in the sPHN domain no longer required an intact amino-terminal Src homology (SH2N) domain or phosphorylation of tyrosine 775 or 783 for activation. These data are consistent with a model in which the SH2C domain is blocked by an intramolecular interaction(s) that is released upon cellular activation by occupancy of the SH2N domain.
With recent developments in the field of tissue engineering (TE), innovative products are seeking... more With recent developments in the field of tissue engineering (TE), innovative products are seeking access to the market to be applied in patients. Therefore, a framework has to be defined in which tissue-engineered products can prove their safety and effectiveness. For these products, the challenge to live up to the standards of drug development arises, not only with respect to practical implementation but also with respect to legislation and ethics. Within this chapter, an overview is given on the development of the standards for this new class of products and on the current status of regulation and legislation in this rapidly changing field.
During the past decade, a large number of cell-based medicinal products have been tested in clini... more During the past decade, a large number of cell-based medicinal products have been tested in clinical trials for the treatment of various diseases and tissue defects. However, licensed products and those approaching marketing authorization are still few. One major area of challenge is the manufacturing and quality development of these complex products, for which significant manipulation of cells might be required. While the paradigms of quality, safety and efficacy must apply also to these innovative products, their demonstration may be demanding. Demonstration of comparability between production processes and batches may be difficult for cell-based medicinal products. Thus, the development should be built around a well-controlled manufacturing process and a qualified product to guarantee reproducible data from nonclinical and clinical studies.
The current White paper summarizes the discussions and exchange of experiences during the first E... more The current White paper summarizes the discussions and exchange of experiences during the first European Interdisciplinary Summit on Cell-Based ATMPs held in Vienna, Austria, May 02-03, 2013. The meeting was supported by the Research Networking Programme REMEDIC (regenerative medicine) funded by the European Science Foundation and by the British Medical Research Council. To improve the competitiveness of Europe in the field of cell-based Advanced Medicinal Therapy Products (ATMPs), the following key issues were identified during the meeting: removal of national hurdles in the European Union, harmonization of national and subnational differences in Hospital Exemption rules, improved treatment algorithms for reimbursement, better knowledge on the mode of action, predictive preclinical efficacy and safety testing, need for innovative systems for preclinical testing, appropriate product characterization, manufacturing with cost of goods in mind, and appropriate design of clinical trials.
Identification of the major components, how these interact with each other, and the modifications... more Identification of the major components, how these interact with each other, and the modifications that follow in the sequence of events triggered by the receptor with high affinity for IgE, is progressing rapidly. A new challenge is to understand these interactions quantitatively. We present the fundamentals of the mechanistic model we are testing through mathematical modeling. The object is to see if the predictions of the model fit with the experimental results.
Numerous signaling molecules associate with lipid rafts, either constitutively or after engagemen... more Numerous signaling molecules associate with lipid rafts, either constitutively or after engagement of surface receptors. One such molecule, phospholipase Cγ-1 (PLCγ1), translocates from the cytosol to lipid rafts during T-cell receptor (TCR) signaling. To investigate the role played by lipid rafts in the activation of this molecule in T cells, an influenza virus hemagglutinin A (HA)-tagged PLCγ1 was ectopically expressed in Jurkat T cells and targeted to these microdomains by the addition of a dual-acylation signal. Raft-targeted PLCγ1 was constitutively tyrosine phosphorylated and induced constitutive NF-AT-dependent transcription and interleukin-2 secretion in Jurkat cells. Tyrosine phosphorylation of raft-targeted PLCγ1 did not require Zap-70 or the interaction with the adapters Lat and Slp-76, molecules that are necessary for TCR signaling. In contrast, the Src family kinase Lck was required. Coexpression in HEK 293T cells of PLCγ1-HA with Lck or the Tec family kinase Rlk result...
Phospholipase Cγ (PLCγ) is a ubiquitous gatekeeper of calcium mobilization and diacylglycerol-med... more Phospholipase Cγ (PLCγ) is a ubiquitous gatekeeper of calcium mobilization and diacylglycerol-mediated events induced by the activation of Ag and growth factor receptors. The activity of PLCγ is regulated through its controlled membrane translocation and tyrosine (Y) phosphorylation. Four activation-induced tyrosine phosphorylation sites have been previously described (Y472, Y771, Y783, and Y1254), but their specific roles in Ag receptor-induced PLCγ1 activation are not fully elucidated. Unexpectedly, we found that the phosphorylation of a PLCγ1 construct with all four sites mutated to phenylalanine was comparable with that observed with wild-type PLCγ1, suggesting the existence of an unidentified site(s). Sequence alignment with known phosphorylation sites in PLCγ2 indicated homology of PLCγ1 tyrosine residue 775 (Y775) with PLCγ2 Y753, a characterized phosphorylation site. Tyrosine 775 was characterized as a phosphorylation site using phospho-specific anti-Y775 antiserum, and by m...
Aggregation of FcεRI on mast cells and basophils leads to autophosphorylation and increased activ... more Aggregation of FcεRI on mast cells and basophils leads to autophosphorylation and increased activity of the cytosolic protein tyrosine kinase Syk. We investigated the roles of the Src kinase Lyn, the immunoreceptor tyrosine-based activation motifs (ITAMs) on the β and γ subunits of FcεRI, and Syk itself in the activation of Syk. Our approach was to build a detailed mathematical model of reactions involving FcεRI, Lyn, Syk, and a bivalent ligand that aggregates FcεRI. We applied the model to experiments in which covalently cross-linked IgE dimers stimulate rat basophilic leukemia cells. The model makes it possible to test the consistency of mechanistic assumptions with data that alone provide limited mechanistic insight. For example, the model helps sort out mechanisms that jointly control dephosphorylation of receptor subunits. In addition, interpreted in the context of the model, experimentally observed differences between the β- and γ-chains with respect to levels of phosphorylati...
Elsevier has created a COVID-19 resource centre with free information in English and Mandarin on ... more Elsevier has created a COVID-19 resource centre with free information in English and Mandarin on the novel coronavirus COVID-19. The COVID-19 resource centre is hosted on Elsevier Connect, the company's public news and information website. Elsevier hereby grants permission to make all its COVID-19-related research that is available on the COVID-19 resource centre-including this research content-immediately available in PubMed Central and other publicly funded repositories, such as the WHO COVID database with rights for unrestricted research re-use and analyses in any form or by any means with acknowledgement of the original source. These permissions are granted for free by Elsevier for as long as the COVID-19 resource centre remains active.
This article has been peer-reviewed and accepted for publication, but has yet to undergo copyedit... more This article has been peer-reviewed and accepted for publication, but has yet to undergo copyediting and proof correction. The final published version may differ from this proof. Human Gene Therapy Clinical Development and Commercialization of Advanced Therapy Medicinal Products (ATMPs) in the EU: how are the product pipeline and regulatory framework evolving?
Growing interest in extracellular vesicles (EVs, including exosomes and microvesicles) as therape... more Growing interest in extracellular vesicles (EVs, including exosomes and microvesicles) as therapeutic entities, particularly in stem cell-related approaches, has underlined the need for standardization and coordination of development efforts. Members of the International Society for Extracellular Vesicles and the Society for Clinical Research and Translation of Extracellular Vesicles Singapore convened a Workshop on this topic to discuss the opportunities and challenges associated with development of EV-based therapeutics at the preclinical and clinical levels. This review outlines topic-specific action items that, if addressed, will enhance the development of best-practice models for EV therapies. Stem Cells Translational Medicine 2017.
Extracellular vesicles (EVs), such as exosomes and microvesicles, are released by different cell ... more Extracellular vesicles (EVs), such as exosomes and microvesicles, are released by different cell types and participate in physiological and pathophysiological processes. EVs mediate intercellular communication as cell-derived extracellular signalling organelles that transmit specific information from their cell of origin to their target cells. As a result of these properties, EVs of defined cell types may serve as novel tools for various therapeutic approaches, including (a) anti-tumour therapy, (b) pathogen vaccination, (c) immune-modulatory and regenerative therapies and (d) drug delivery. The translation of EVs into clinical therapies requires the categorization of EV-based therapeutics in compliance with existing regulatory frameworks. As the classification defines subsequent requirements for manufacturing, quality control and clinical investigation, it is of major importance to define whether EVs are considered the active drug components or primarily serve as drug delivery vehi...
The management of clinical trial applications by public authorities is a complex process involvin... more The management of clinical trial applications by public authorities is a complex process involving several regulations, actors, and IT systems. In this paper we present a modeling approach based on semantic information models that supports this process. In particular, the approach can be used for the generation of user-centric visualizations, performance and compliance analyses and the distribution of the contained knowledge within an organization and to third parties. The approach has been developed together with AGES PharmMed and applied to their core processes.
Semantic Technologies for Business and Information Systems Engineering
The use of semantic technologies in practical scenarios requires carefully balancing the tradeoff... more The use of semantic technologies in practical scenarios requires carefully balancing the tradeoff between costs and benefits in order to gain acceptance. In this chapter we report on a project conducted together with the Austrian competent authority in regard to safety in healthcare. It is described how semantic technologies can be combined with conceptual models to support management executives in the distribution of knowledge and the analysis of compliance. The approach is based on a step-wise semantic enrichment of conceptual models with formal semantic schemata in order to support human analyses. It has been implemented on the ADONIS meta modeling platform and applied to a scenario dealing with the management of applications for clinical trials.
Advances in Experimental Medicine and Biology, 2015
With the release of Regulation 1394/2007, a new framework for gene and cell therapy medicinal pro... more With the release of Regulation 1394/2007, a new framework for gene and cell therapy medicinal products and tissue-engineered products was established in the European Union. For all three product classes, called advanced therapy medicinal products, a centralised marketing authorisation became mandatory. The European Medicines Agency (EMA) together with its Committee for Advanced Therapies, Committee for Human Medicinal Products and the network of national agencies is responsible for scientific evaluation of the marketing authorisation applications. For a new application, data and information relating to manufacturing processes and quality control of the active substance and the final product have to be submitted for evaluation together with data from non-clinical and clinical safety and efficacy studies. Technical requirements for ATMPs are defined in the legislation, and guidance for different products is available through several EMA/CAT guidelines. Due to the diversity of ATMPs, a tailored approach for regulating these products is considered necessary. Thus, a risk-based approach has been introduced for ATMPs allowing flexibility for the regulatory requirements. Since the regulatory framework for ATMPs was established, five products have been licenced in the European Union. However, the pipeline of new ATMPs is much bigger, as seen from the significant numbers of different products discussed by the CAT in scientific advice and classification procedures. In 2013, a public consultation on the ATMP Regulation was conducted by the European Commission, and the results were published in 2014. The report proposes several improvements for the current framework and established procedures for the regulation of ATMPs.
In this paper we describe a modeling method for supporting performance management by building upo... more In this paper we describe a modeling method for supporting performance management by building upon the current challenges of public health authorities. Through focusing on the performance management requirements of national competent authorities (NCA) that fulfill several duties in regard to the marketing authorization of medicinal products, we derive a modeling language, an according modeling procedure and mechanisms and algorithms. Thereby, particular requirements in regard to the compliance to legal regulations, the competition of NCAs within the European Union, the allocation of resources under uncertainty, and the specific human resource requirements of NCAs have to be taken into account. The modeling language is formally described using a meta model based approach and implemented on a meta modeling platform. For the evaluation, the modeling method has been applied in a scientific study with the Austrian national competent authority AGES PharmMed.
On September 11, 2014, a workshop entitled ‘Advanced Therapy Medicinal Products: How to Bring Cel... more On September 11, 2014, a workshop entitled ‘Advanced Therapy Medicinal Products: How to Bring Cell-Based Medicinal Product Successfully to the Market' was held at the 47th annual meeting of the German Society for Transfusion Medicine and Immunohematology (DGTI), co-organised by the European Medicines Agency (EMA) and the DGTI in collaboration with the German Stem Cell Network (GSCN). The workshop brought together over 160 participants from academia, hospitals, small- or medium-sized enterprise developers and regulators. At the workshop, speakers from EMA, the Committee for Advanced Therapies (CAT), industry and academia addressed the regulatory aspects of development and authorisation of advanced therapy medicinal products (ATMPs), classification of ATMPs and considerations on cell-based therapies for cardiac repair. The open forum discussion session allowed for a direct interaction between ATMP developers and the speakers from EMA and CAT.
Phosphoinositide-specific phospholipase C-gamma1 (PLC-gamma1) is a key enzyme that governs cellul... more Phosphoinositide-specific phospholipase C-gamma1 (PLC-gamma1) is a key enzyme that governs cellular functions such as gene transcription, secretion, proliferation, motility, and development. Here, we show that PLC-gamma1 is regulated via a novel autoinhibitory mechanism involving its carboxy-terminal Src homology (SH2C) domain. Mutation of the SH2C domain tyrosine binding site led to constitutive PLC-gamma1 activation. The amino-terminal split pleckstrin homology (sPHN) domain was found to regulate the accessibility of the SH2C domain. PLC-gamma1 constructs with mutations in tyrosine 509 and phenylalanine 510 in the sPHN domain no longer required an intact amino-terminal Src homology (SH2N) domain or phosphorylation of tyrosine 775 or 783 for activation. These data are consistent with a model in which the SH2C domain is blocked by an intramolecular interaction(s) that is released upon cellular activation by occupancy of the SH2N domain.
With recent developments in the field of tissue engineering (TE), innovative products are seeking... more With recent developments in the field of tissue engineering (TE), innovative products are seeking access to the market to be applied in patients. Therefore, a framework has to be defined in which tissue-engineered products can prove their safety and effectiveness. For these products, the challenge to live up to the standards of drug development arises, not only with respect to practical implementation but also with respect to legislation and ethics. Within this chapter, an overview is given on the development of the standards for this new class of products and on the current status of regulation and legislation in this rapidly changing field.
During the past decade, a large number of cell-based medicinal products have been tested in clini... more During the past decade, a large number of cell-based medicinal products have been tested in clinical trials for the treatment of various diseases and tissue defects. However, licensed products and those approaching marketing authorization are still few. One major area of challenge is the manufacturing and quality development of these complex products, for which significant manipulation of cells might be required. While the paradigms of quality, safety and efficacy must apply also to these innovative products, their demonstration may be demanding. Demonstration of comparability between production processes and batches may be difficult for cell-based medicinal products. Thus, the development should be built around a well-controlled manufacturing process and a qualified product to guarantee reproducible data from nonclinical and clinical studies.
The current White paper summarizes the discussions and exchange of experiences during the first E... more The current White paper summarizes the discussions and exchange of experiences during the first European Interdisciplinary Summit on Cell-Based ATMPs held in Vienna, Austria, May 02-03, 2013. The meeting was supported by the Research Networking Programme REMEDIC (regenerative medicine) funded by the European Science Foundation and by the British Medical Research Council. To improve the competitiveness of Europe in the field of cell-based Advanced Medicinal Therapy Products (ATMPs), the following key issues were identified during the meeting: removal of national hurdles in the European Union, harmonization of national and subnational differences in Hospital Exemption rules, improved treatment algorithms for reimbursement, better knowledge on the mode of action, predictive preclinical efficacy and safety testing, need for innovative systems for preclinical testing, appropriate product characterization, manufacturing with cost of goods in mind, and appropriate design of clinical trials.
Identification of the major components, how these interact with each other, and the modifications... more Identification of the major components, how these interact with each other, and the modifications that follow in the sequence of events triggered by the receptor with high affinity for IgE, is progressing rapidly. A new challenge is to understand these interactions quantitatively. We present the fundamentals of the mechanistic model we are testing through mathematical modeling. The object is to see if the predictions of the model fit with the experimental results.
Numerous signaling molecules associate with lipid rafts, either constitutively or after engagemen... more Numerous signaling molecules associate with lipid rafts, either constitutively or after engagement of surface receptors. One such molecule, phospholipase Cγ-1 (PLCγ1), translocates from the cytosol to lipid rafts during T-cell receptor (TCR) signaling. To investigate the role played by lipid rafts in the activation of this molecule in T cells, an influenza virus hemagglutinin A (HA)-tagged PLCγ1 was ectopically expressed in Jurkat T cells and targeted to these microdomains by the addition of a dual-acylation signal. Raft-targeted PLCγ1 was constitutively tyrosine phosphorylated and induced constitutive NF-AT-dependent transcription and interleukin-2 secretion in Jurkat cells. Tyrosine phosphorylation of raft-targeted PLCγ1 did not require Zap-70 or the interaction with the adapters Lat and Slp-76, molecules that are necessary for TCR signaling. In contrast, the Src family kinase Lck was required. Coexpression in HEK 293T cells of PLCγ1-HA with Lck or the Tec family kinase Rlk result...
Phospholipase Cγ (PLCγ) is a ubiquitous gatekeeper of calcium mobilization and diacylglycerol-med... more Phospholipase Cγ (PLCγ) is a ubiquitous gatekeeper of calcium mobilization and diacylglycerol-mediated events induced by the activation of Ag and growth factor receptors. The activity of PLCγ is regulated through its controlled membrane translocation and tyrosine (Y) phosphorylation. Four activation-induced tyrosine phosphorylation sites have been previously described (Y472, Y771, Y783, and Y1254), but their specific roles in Ag receptor-induced PLCγ1 activation are not fully elucidated. Unexpectedly, we found that the phosphorylation of a PLCγ1 construct with all four sites mutated to phenylalanine was comparable with that observed with wild-type PLCγ1, suggesting the existence of an unidentified site(s). Sequence alignment with known phosphorylation sites in PLCγ2 indicated homology of PLCγ1 tyrosine residue 775 (Y775) with PLCγ2 Y753, a characterized phosphorylation site. Tyrosine 775 was characterized as a phosphorylation site using phospho-specific anti-Y775 antiserum, and by m...
Aggregation of FcεRI on mast cells and basophils leads to autophosphorylation and increased activ... more Aggregation of FcεRI on mast cells and basophils leads to autophosphorylation and increased activity of the cytosolic protein tyrosine kinase Syk. We investigated the roles of the Src kinase Lyn, the immunoreceptor tyrosine-based activation motifs (ITAMs) on the β and γ subunits of FcεRI, and Syk itself in the activation of Syk. Our approach was to build a detailed mathematical model of reactions involving FcεRI, Lyn, Syk, and a bivalent ligand that aggregates FcεRI. We applied the model to experiments in which covalently cross-linked IgE dimers stimulate rat basophilic leukemia cells. The model makes it possible to test the consistency of mechanistic assumptions with data that alone provide limited mechanistic insight. For example, the model helps sort out mechanisms that jointly control dephosphorylation of receptor subunits. In addition, interpreted in the context of the model, experimentally observed differences between the β- and γ-chains with respect to levels of phosphorylati...
Uploads
Papers by Ilona Reischl