TY - JOUR
T1 - PDGF stimulates tyrosine phosphorylation of JAK 1 protein tyrosine kinase in human mesangial cells
AU - Choudhury, Goutam Ghosh
AU - Marra, Fabio
AU - Kiyomoto, Hideyasu
AU - Abboud, Hanna E.
N1 - Funding Information:
This study was supported in part by VA Medical Research Service and NIH grants DK 43988 and DK 33665 to HEA and a grant in aid from the AHA-Texas affiliate to GGC. We thank Sergio Garcia for help with the cell culture.
PY - 1996
Y1 - 1996
N2 - Platelet-derived growth factor (PDGF) exerts multiple effects in glomerular mesangial cells, including transcription of genes that mediate its biological activity. We have partially characterized PDGF-mediated early mitogenic signal transduction pathways that include activation of protein kinase Cα and phosphatidylinositol 3 kinase. However, the precise mechanism of PDGF-induced gene transcription is not yet clear. A family of cytoplasmic transcription factors referred to as signal transducers and activators of transcription (STAT) has recently been identified. This group of transcription factors is activated by different cytokines via tyrosine phosphorylation. We studied the effect of PDGF on STATs in human mesangial cells. Using a gel retardation assay, nuclear and cytoplasmic extracts from PDGF-stimulated mesangial cells contained protein factors that bind to a DNA sequence representing the sis-inducible element (SIE) present in the c-fos gene promoter. These protein factors also bind to the enhancer element present in interferon-γ responsive genes, suggesting the involvement of STAT proteins. The addition of monoclonal antibody that recognizes STAT 1 results in 'supershift' of the DNA-protein complex stimulated by PDGF indicating the presence of STAT 1. Immunoblotting experiments with a monoclonal STAT 1 antibody revealed the presence of STAT1α and STAT1β in mesangial cells. Since certain cytokines activate STATs via tyrosine phosphorylation mediated by JAK family of tyrosine kinases, we studied the effect of PDGF on JAK kinases. Antiphosphotyrosine immunoblotting of JAK 1 immunoprecipitates from PDGF-stimulated mesangial cell lysate showed increased tyrosine phosphorylation of this tyrosine kinase. In vitro immune complex kinase assay of JAK 1 immunoprecipitates from PDGF-stimulated mesangial cell lysate revealed activation of this tyrosine kinase. Taken together, these data demonstrate that PDGF activates the transcription factor STAT 1 in mesangial cells. The data also provide the first evidence that PDGF stimulates tyrosine phosphorylation of JAK 1, the cytoplasmic tyrosine kinase stimulated by many other cytokines to activate transcription via STATs. These observations indicate that JAK 1 is a downstream tyrosine kinase in PDGF receptor signaling and is a candidate for activation of STAT 1.
AB - Platelet-derived growth factor (PDGF) exerts multiple effects in glomerular mesangial cells, including transcription of genes that mediate its biological activity. We have partially characterized PDGF-mediated early mitogenic signal transduction pathways that include activation of protein kinase Cα and phosphatidylinositol 3 kinase. However, the precise mechanism of PDGF-induced gene transcription is not yet clear. A family of cytoplasmic transcription factors referred to as signal transducers and activators of transcription (STAT) has recently been identified. This group of transcription factors is activated by different cytokines via tyrosine phosphorylation. We studied the effect of PDGF on STATs in human mesangial cells. Using a gel retardation assay, nuclear and cytoplasmic extracts from PDGF-stimulated mesangial cells contained protein factors that bind to a DNA sequence representing the sis-inducible element (SIE) present in the c-fos gene promoter. These protein factors also bind to the enhancer element present in interferon-γ responsive genes, suggesting the involvement of STAT proteins. The addition of monoclonal antibody that recognizes STAT 1 results in 'supershift' of the DNA-protein complex stimulated by PDGF indicating the presence of STAT 1. Immunoblotting experiments with a monoclonal STAT 1 antibody revealed the presence of STAT1α and STAT1β in mesangial cells. Since certain cytokines activate STATs via tyrosine phosphorylation mediated by JAK family of tyrosine kinases, we studied the effect of PDGF on JAK kinases. Antiphosphotyrosine immunoblotting of JAK 1 immunoprecipitates from PDGF-stimulated mesangial cell lysate showed increased tyrosine phosphorylation of this tyrosine kinase. In vitro immune complex kinase assay of JAK 1 immunoprecipitates from PDGF-stimulated mesangial cell lysate revealed activation of this tyrosine kinase. Taken together, these data demonstrate that PDGF activates the transcription factor STAT 1 in mesangial cells. The data also provide the first evidence that PDGF stimulates tyrosine phosphorylation of JAK 1, the cytoplasmic tyrosine kinase stimulated by many other cytokines to activate transcription via STATs. These observations indicate that JAK 1 is a downstream tyrosine kinase in PDGF receptor signaling and is a candidate for activation of STAT 1.
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U2 - 10.1038/ki.1996.3
DO - 10.1038/ki.1996.3
M3 - Article
C2 - 8770944
AN - SCOPUS:0030053935
VL - 49
SP - 19
EP - 25
JO - Kidney International
JF - Kidney International
SN - 0085-2538
IS - 1
ER -