Gq-dependent signaling upregulates COX2 in glomerular podocytes.
Accumulating evidence suggests that upregulation of cyclooxygenase 2 (COX2) in glomerular podocytes promotes podocyte injury. Because Gq signaling activates calcineurin and calcineurin-dependent mechanisms are known to mediate COX2 expression, this study investigated the role of Gqalpha in promoting COX2 expression in podocytes. A constitutively active Gq alpha subunit tagged with the TAT HIV protein sequence was introduced into an immortalized podocyte cell line by protein transduction. This stimulated inositol trisphosphate production, activated an nuclear factor of activated T cells-responsive reporter construct, and enhanced levels of both COX2 mRNA and protein compared with cells treated with a Gq protein lacking the TAT sequence. Induction of COX2 was associated with increased prostaglandin E(2) production and podocyte death, both of which were attenuated by selective COX2 inhibition. In vivo, levels of COX2 mRNA and protein were significantly enhanced in podocytes from transgenic mice that expressed podocyte-targeted constitutively active Gqalpha compared with nontransgenic littermates. These data suggest that Gq-dependent signaling cascades stimulate calcineurin and, in turn, upregulate COX2 mRNA and protein, increase eicosanoid production, and cause podocyte injury.
Wang
Liming
L
Division of Nephrology, Department of Medicine, Duke University, Durham VA Medical Center, Durham, NC 27710, USA.
Flannery
Patrick J
PJ
Rosenberg
Paul B
PB
Fields
Timothy A
TA
Spurney
Robert F
RF
D000818:Animals; D001483:Base Sequence; D019703:Calcineurin / Q000378:metabolism; D016923:Cell Death; D002460:Cell Line; D051546:Cyclooxygenase 2 / Q000235:genetics* / Q000378:metabolism*; D018076:DNA, Complementary / Q000235:genetics; D015232:Dinoprostone / Q000096:biosynthesis; D043802:GTP-Binding Protein alpha Subunits, Gq-G11 / Q000235:genetics / Q000378:metabolism*; D015544:Inositol 1,4,5-Trisphosphate / Q000096:biosynthesis; D051379:Mice; D008822:Mice, Transgenic; D050778:NFATC Transcription Factors / Q000378:metabolism; D050199:Podocytes / Q000378:metabolism* / Q000473:pathology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D015854:Up-Regulation; D054322:tat Gene Products, Human Immunodeficiency Virus / Q000235:genetics
D018076:DNA, Complementary; D050778:NFATC Transcription Factors; D012333:RNA, Messenger; D011994:Recombinant Proteins; D054322:tat Gene Products, Human Immunodeficiency Virus; D015544:Inositol 1,4,5-Trisphosphate; C077623:Ptgs2 protein, mouse; D051546:Cyclooxygenase 2; D019703:Calcineurin; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D015232:Dinoprostone