title: P2X7 receptor activation regulates rapid unconventional export of transglutaminase-2.
abstract: Transglutaminases (denoted TG or TGM) are externalized from cells via an unknown unconventional secretory pathway. Here, we show for the first time that purinergic signaling regulates active secretion of TG2 (also known as TGM2), an enzyme with a pivotal role in stabilizing extracellular matrices and modulating cell-matrix interactions in tissue repair. Extracellular ATP promotes TG2 secretion by macrophages, and this can be blocked by a selective antagonist against the purinergic receptor P2X7 (P2X7R, also known as P2RX7). Introduction of functional P2X7R into HEK293 cells is sufficient to confer rapid, regulated TG2 export. By employing pharmacological agents, TG2 release could be separated from P2X7R-mediated microvesicle shedding. Neither Ca(2+) signaling alone nor membrane depolarization triggered TG2 secretion, which occurred only upon receptor membrane pore formation and without pannexin channel involvement. A gain-of-function mutation in P2X7R associated with autoimmune disease caused enhanced TG2 externalization from cells, and this correlated with increased pore activity. These results provide a mechanistic explanation for a link between active TG2 secretion and inflammatory responses, and aberrant enhanced TG2 activity in certain autoimmune conditions.
authors.affiliation: Matrix Biology & Tissue Repair Research Unit and Arthritis Research UK Biomechanics and Bioengineering Center of Excellence, College of Biomedical and Life Sciences, Cardiff University, Cardiff CF14 4XY, UK AdamczykM@Cardiff.ac.uk AeschlimannDP@Cardiff.ac.uk.
authors.forename: Magdalena
authors.initials: M
authors.lastname: Adamczyk
authors.affiliation: Matrix Biology & Tissue Repair Research Unit and Arthritis Research UK Biomechanics and Bioengineering Center of Excellence, College of Biomedical and Life Sciences, Cardiff University, Cardiff CF14 4XY, UK.
authors.forename: Rhiannon
authors.initials: R
authors.lastname: Griffiths
authors.affiliation: Matrix Biology & Tissue Repair Research Unit and Arthritis Research UK Biomechanics and Bioengineering Center of Excellence, College of Biomedical and Life Sciences, Cardiff University, Cardiff CF14 4XY, UK.
authors.forename: Sharon
authors.initials: S
authors.lastname: Dewitt
authors.affiliation: Matrix Biology & Tissue Repair Research Unit and Arthritis Research UK Biomechanics and Bioengineering Center of Excellence, College of Biomedical and Life Sciences, Cardiff University, Cardiff CF14 4XY, UK.
authors.forename: Vera
authors.initials: V
authors.lastname: Knäuper
authors.affiliation: Matrix Biology & Tissue Repair Research Unit and Arthritis Research UK Biomechanics and Bioengineering Center of Excellence, College of Biomedical and Life Sciences, Cardiff University, Cardiff CF14 4XY, UK AdamczykM@Cardiff.ac.uk AeschlimannDP@Cardiff.ac.uk.
authors.forename: Daniel
authors.initials: D
authors.lastname: Aeschlimann
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D001327:Autoimmune Diseases / Q000235:genetics / Q000378:metabolism; D020013:Calcium Signaling; D045744:Cell Line, Tumor; D005260:Female; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D008297:Male; D008564:Membrane Potentials; D009154:Mutation; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D058486:Receptors, Purinergic P2X7 / Q000235:genetics / Q000378:metabolism*; D011503:Transglutaminases / Q000235:genetics / Q000378:metabolism*
chemical_list: C546468:P2RX7 protein, human; D058486:Receptors, Purinergic P2X7; C000717608:TGM2 protein, human; D000255:Adenosine Triphosphate; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D011503:Transglutaminases; D019204:GTP-Binding Proteins
keywords: Extracellular matrix stabilization; Innate immunity; P2X7 receptor; Purinergic signaling; Transglutaminase; Unconventional protein secretion