Activated STAT1 suppresses proliferation of cultured rat mesangial cells.
BACKGROUND
JAK-STAT signaling has been shown to promote development and proliferation in lymphopoietic and hematopoietic lineages. We investigated the effect of activated STAT1 on mesangial cell proliferation.


METHODS
Rat mesangial cells of primary culture (rMCs) were used in the following experiments: (1) Whole cell lysates were immunoblotted against JAK1 and JAK2. (2) Whole cell lysates and nuclear proteins were extracted from rMCs with or without treatment with interferon-gamma, and immunoblotting was performed against both STAT1 and tyrosine (701)-phosphorylated STAT1. (3) rMCs and rMCs electroporated with either wild-type STAT1, mutated STAT1, or antibody against STAT1 were incubated with interferon-gamma for 20 hours, followed by a further incubation with [3H]-thymidine for four hours.


RESULTS
JAK1, JAK2, and STAT1 were detected in whole cell lysates, suggesting that JAK-STAT signaling could be activated by interferon-gamma (INF-gamma). Using an antibody specific for tyrosine-phosphorylated STAT1, we detected signal in the INF-gamma-treated nuclear extracts, which showed translocation of phosphorylated STAT1 to the nucleus. [3H]-thymidine incorporation in the presence of INF-gamma was significantly lower than that of control in a dose-dependent manner. The introduction of wild-type STAT1 enhanced the effect of interferon-gamma and decreased [3H]-thymidine incorporation, whereas tyrosine-mutated (Y701F) STAT1 and SH2 domain (R602T)-mutated STAT1 reversed INF-gamma-induced suppression of [3H]-thymidine incorporation. Electroinjected antibody against STAT1 increased [3H]-thymidine incorporation upon stimulation with INF-gamma.


CONCLUSIONS
STAT1 activated by interferon-gamma suppresses mesangial cell proliferation.
Nakashima
O
O
Second Department of Internal Medicine and First Department of Internal Medicine, Tokyo Medical and Dental University, Tokyo, Japan.
Terada
Y
Y
Hanada
S
S
Yamamoto
K
K
Kuwahara
M
M
Sasaki
S
S
Marumo
F
F
D000818:Animals; D002455:Cell Division / Q000502:physiology; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000378:metabolism / Q000502:physiology*; D005920:Glomerular Mesangium / Q000166:cytology* / Q000378:metabolism; D007371:Interferon-gamma / Q000378:metabolism; D053613:Janus Kinase 1; D053614:Janus Kinase 2; D051379:Mice; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins; D051381:Rats; D050794:STAT1 Transcription Factor; D013936:Thymidine / Q000037:antagonists & inhibitors; D015534:Trans-Activators / Q000378:metabolism / Q000502:physiology*
D004268:DNA-Binding Proteins; D011518:Proto-Oncogene Proteins; D050794:STAT1 Transcription Factor; C494080:Stat1 protein, mouse; C494081:Stat1 protein, rat; D015534:Trans-Activators; D007371:Interferon-gamma; D011505:Protein-Tyrosine Kinases; C507905:Jak1 protein, mouse; C507906:Jak1 protein, rat; C507926:Jak2 protein, mouse; C507927:Jak2 protein, rat; D053613:Janus Kinase 1; D053614:Janus Kinase 2; D013936:Thymidine