Activation of Stat3 in endothelial cells following hypoxia-reoxygenation is mediated by Rac1 and protein Kinase C.
Stat3 is an important transcription factor that regulates both proinflammatory and anit-apoptotic pathways in the heart. This study examined the mechanisms of activation of Stat3 in human endothelial cells following hypoxia/reoxygenation (H/R). By expression of constitutively active Rac1 mutant protein, and by RNA silencing of Rac1, we found that Stat3 forms a multiprotein complex with Rac1 and PKC in an H/R-dependent manner, which at least in part, appears to regulate Stat3 S727 phosphorylation. Selective inhibition of PKC with calphostin C produces a marked suppression of Stat3 S727 phosphorylation. The association of Stat3 with Rax1 occurs predominantly at the cell membrane, but also inside the nucleus, and occurs through the binding of the coiled-coil domain of Stat3 to the 54 NH(2)-terminal residues of Rac1. Transfection with a peptide comprising the NH(2)-terminal 17 amino acid residues of Rac1-dependent signaling pathways resulting in physical association between Rac1 and Stat3 and the formation of a novel multiprotein complex with PKC.
Division of Cardiology, Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
Subhendra N
SN
Mattagajasingh
Xiao Ping
XP
Yang
Kaikobad
K
Irani
Ilwola
I
Mattagajasingh
Lewis C
LC
Becker
D000111:Acetylcysteine / Q000494:pharmacology; D015687:Cell Hypoxia / Q000187:drug effects; D002462:Cell Membrane / Q000187:drug effects / Q000201:enzymology; D002467:Cell Nucleus / Q000187:drug effects / Q000201:enzymology; D055785:Gene Knockdown Techniques; D061307:Human Umbilical Vein Endothelial Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D010100:Oxygen / Q000494:pharmacology*; D010455:Peptides / Q000737:chemistry / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D010768:Phosphoserine / Q000378:metabolism; D019000:Phosphotyrosine / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects; D011493:Protein Kinase C / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D021381:Protein Transport / Q000187:drug effects; D034741:RNA, Small Interfering / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D050796:STAT3 Transcription Factor / Q000737:chemistry / Q000378:metabolism*; D014162:Transfection; D020830:rac1 GTP-Binding Protein / Q000737:chemistry / Q000378:metabolism*; D000099221:Protein Kinase C zeta
D000111:Acetylcysteine; D010100:Oxygen; D010455:Peptides; D010768:Phosphoserine; D019000:Phosphotyrosine; D011493:Protein Kinase C; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; D050796:STAT3 Transcription Factor; D020830:rac1 GTP-Binding Protein; D000099221:Protein Kinase C zeta; C494086:STAT3 protein, human