T Karhu1, K Akiyama2, O Vuolteenaho3, U Bergmann4, T Naito5, K Tatemoto1, K-H Herzig6. 1. Research Unit of Biomedicine, University of Oulu, Oulu, Finland; Biocenter Oulu, University of Oulu, Oulu, Finland. 2. Okinawa Institute of Science and Technology Graduate University, Tancha, Onna-son, Kunigami, Okinawa, Japan. 3. Research Unit of Biomedicine, University of Oulu, Oulu, Finland; Nordlab Oulu, Oulu, Finland. 4. Biocenter Oulu, University of Oulu, Oulu, Finland; Faculty of Biochemistry and Molecular Medicine, University of Oulu, Oulu, Finland. 5. Okinawa Institute of Science and Technology Graduate University, Tancha, Onna-son, Kunigami, Okinawa, Japan; Research Institute of Natural-Drug Leads, Kanagawa University, Hiratsuka, Kanagawa, Japan. 6. Research Unit of Biomedicine, University of Oulu, Oulu, Finland; Biocenter Oulu, University of Oulu, Oulu, Finland; Department of Gastroenterology and Metabolism, Poznan University of Medical Sciences, Poznan, Poland; Medical Research Center (MRC), Oulu, Finland; Oulu University Hospital, Oulu, Finland. Electronic address: Karl-Heinz.Herzig@oulu.fi.
Abstract
BACKGROUND: Mast cells are important modulators of the human immune system via their release of several inflammatory mediators and proteases. The release can be activated by different pathways: the classical immunoglobulin E-dependent pathway and by the non-immunological immunoglobulin E-independent pathway. MAS-related G protein-coupled receptor X2 (MRGPRX2) is expressed in mast cells and it is one of the endogenous receptor responsible for the IgE-independent activation of human mast cell. The MRGPRX2 is classified as orphan receptor and unlike most GPCRs, the MRGPRX2 recognizes a wide range of basic molecules. Thus, there still might be several unknown ligands for the receptor. METHODS: MRGPRX2 activating peptides were isolated from human plasma using consecutive HPLC purification steps. The isolation process was monitored with MRGPRX2 transfected HEK 293 cells. The isolated peptides were sequenced by MS and synthetized. The synthetic peptides were used to determine degranulation of the human LAD 2 mast cell line by measuring β-hexosaminidase release. RESULTS: Three endogenous MRGPRX2 activating peptides were isolated from human plasma. These peptides are identified as fragments of albumin. The isolated fragments activate MRGPRX2 and degranulate MRGPRX2 expressing LAD 2 cells in dose-dependent manner. CONCLUSIONS: The isolated basic peptides generated from human albumin are able to degranulate mast cells via the MRGPRX2. GENERAL SIGNIFICANCE: These endogenous albumin fragments, cleaved from albumin by mast cell secreted proteases, provide a possible pathway for self-perpetuating mast cell dependent inflammation.
BACKGROUND: Mast cells are important modulators of the human immune system via their release of several inflammatory mediators and proteases. The release can be activated by different pathways: the classical immunoglobulin E-dependent pathway and by the non-immunological immunoglobulin E-independent pathway. MAS-related G protein-coupled receptor X2 (MRGPRX2) is expressed in mast cells and it is one of the endogenous receptor responsible for the IgE-independent activation of human mast cell. The MRGPRX2 is classified as orphan receptor and unlike most GPCRs, the MRGPRX2 recognizes a wide range of basic molecules. Thus, there still might be several unknown ligands for the receptor. METHODS:MRGPRX2 activating peptides were isolated from human plasma using consecutive HPLC purification steps. The isolation process was monitored with MRGPRX2 transfected HEK 293 cells. The isolated peptides were sequenced by MS and synthetized. The synthetic peptides were used to determine degranulation of the human LAD 2 mast cell line by measuring β-hexosaminidase release. RESULTS: Three endogenous MRGPRX2 activating peptides were isolated from human plasma. These peptides are identified as fragments of albumin. The isolated fragments activate MRGPRX2 and degranulate MRGPRX2 expressing LAD 2 cells in dose-dependent manner. CONCLUSIONS: The isolated basic peptides generated from human albumin are able to degranulate mast cells via the MRGPRX2. GENERAL SIGNIFICANCE: These endogenous albumin fragments, cleaved from albumin by mast cell secreted proteases, provide a possible pathway for self-perpetuating mast cell dependent inflammation.
Authors: Tony L Yaksh; Kelly A Eddinger; Shinichi Kokubu; Zhenping Wang; Anna DiNardo; Roshni Ramachandran; Yuelian Zhu; Yajun He; Fieke Weren; Daphne Quang; Shelle A Malkmus; Katherine Lansu; Wesley K Kroeze; Brian Eliceiri; Joanne J Steinauer; Peter W Schiller; Peter Gmeiner; Linda M Page; Keith R Hildebrand Journal: Anesthesiology Date: 2019-07 Impact factor: 7.892