Effect of vasoactive agents on induction of Egr-1 in rat mesangial cells: correlation with mitogenicity.
The early growth response gene 1 (Egr-1) is a member of the family of immediate early response genes. Egr-1 encodes a nuclear phosphoprotein that binds a specific nonameric DNA sequence through three zinc-finger domains and functions as a transcriptional activator. We tested whether the vasoactive agents platelet-derived growth factor (PDGF), arginine vasopressin (AVP), serotonin (5-HT), and angiotensin II (ANG II) induced Egr-1 mRNA in cultured rat mesangial cells (MCs) and investigated the role of protein kinase C (PKC) in mediating the induction process. PDGF, AVP, and 5-HT induced Egr-1 mRNA within 15 min, reaching peak levels at 45-60 min. After PDGF and 5-HT stimulation, Egr-1 mRNA levels returned to baseline within 4 h, whereas AVP induced a sustained increase for up to 8 h. There was a very close correlation between doses required for Egr-1 induction and induction of MC proliferation. ANG II was a very weak MC mitogen and induced only a small increase in Egr-1 mRNA. Comparison of control cells with cells depleted of PKC by 48 h of PMA treatment revealed that induction of Egr-1 by PDGF and 5-HT is independent of PKC. In contrast, however, the Egr-1 response to AVP was diminished in PKC-depleted cells. AVP induced Egr-1 mRNA 10.9-fold in control cells, compared with 7.8-fold in PKC-depleted cells. Egr-1 mRNA after AVP stimulation remained elevated in control cells for up to 8 h but returned to baseline after 120 min in PKC-depleted cells. Similar results were obtained using the PKC-inhibitor H-7. Using immunocytochemistry, PDGF and AVP were found to induce Egr-1 protein within 30 min localized to the nucleus. We conclude that there is a strong correlation between induction of Egr-1 after stimulation with PDGF, AVP, 5-HT, and ANG II and the proliferative response elicited by these agents in MCs. AVP induces Egr-1 by both PKC-dependent and PKC-independent pathways, whereas the effects of PDGF and 5-HT are independent of PKC.
Rupprecht
H D
HD
Department of Internal Medicine, Yale University School of Medicine, West Haven, Connecticut.
Dann
P
P
Sukhatme
V P
VP
Sterzel
R B
RB
Coleman
D L
DL
D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D001127:Arginine Vasopressin / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000378:metabolism*; D051766:Early Growth Response Protein 1; D005786:Gene Expression Regulation / Q000187:drug effects*; D005920:Glomerular Mesangium / Q000502:physiology*; D017874:Immediate-Early Proteins; D008297:Male; D008934:Mitogens / Q000494:pharmacology*; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012701:Serotonin / Q000494:pharmacology; D013997:Time Factors; D014157:Transcription Factors / Q000378:metabolism*; D014661:Vasoconstriction / Q000187:drug effects*; D014664:Vasodilation / Q000187:drug effects*
D004268:DNA-Binding Proteins; D051766:Early Growth Response Protein 1; C486110:Egr1 protein, rat; D017874:Immediate-Early Proteins; D008934:Mitogens; D010982:Platelet-Derived Growth Factor; D012333:RNA, Messenger; D014157:Transcription Factors; D000804:Angiotensin II; D001127:Arginine Vasopressin; D012701:Serotonin; D011493:Protein Kinase C