Induction of c-fos protein by activation of vasopressin receptors in smooth muscle cells.
Stimulation of vasopressin (V1) receptors of rat aortic smooth muscle cells (A-10, ATCC CRL 1476) results in the hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP2) to inositol 1,4,5-trisphosphate (IP3) and diacylglycerol (DAG) with the mobilization of intracellular calcium. When A-10 cells are exposed to arginine vasopressin (AVP), there is an increase in the level of c-fos oncoprotein. The extent of induction of c-fos oncoprotein depends on both the time of exposure of the cells to AVP, reaching a maximum at 60 min after which there is a slow decline, and the concentration of AVP used, with an approximate EC50 of 1 nM which corresponds well with the Kd of vasopressin binding to these receptors. This vasopressin-mediated increase in c-fos protein level is inhibited by a V1/V2 antagonist (SKF 101498) suggesting that this is a receptor-mediated event. In addition dDAVP, a V2 selective agonist, is much less effective than AVP in inducing c-fos protein suggesting that AVP mediates its effect via V1 receptors. Desensitization of vasopressin receptors by prolonged exposure to AVP resulted in no additional induction of c-fos protein level in response to second challenge of AVP. In addition to AVP, phorbol dibutyrate (PDBu), an activator of protein kinase C (PKC), also stimulates the accumulation of c-fos protein although to a lesser extent than AVP. The above data suggest that c-fos protein levels in smooth muscle cells are regulated by AVP and the hormonal effect may be mediated through PI turnover and DAG, IP3 and Ca2+ signals.
Nambi
P
P
Department of Molecular Pharmacology, SK&F Laboratories, Philadelphia, PA 19101.
Watt
R
R
Whitman
M
M
Aiyar
N
N
Moore
J P
JP
Evan
G I
GI
Crooke
S
S
D000818:Animals; D001013:Aorta, Thoracic; D001127:Arginine Vasopressin / Q000031:analogs & derivatives / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D003894:Deamino Arginine Vasopressin / Q000494:pharmacology; D004075:Diglycerides / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D006868:Hydrolysis; D015544:Inositol 1,4,5-Trisphosphate; D007295:Inositol Phosphates / Q000378:metabolism; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism*; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology; D019269:Phosphatidylinositol 4,5-Diphosphate; D010716:Phosphatidylinositols / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis*; D016760:Proto-Oncogene Proteins c-fos; D051381:Rats; D011945:Receptors, Angiotensin / Q000502:physiology*; D017483:Receptors, Vasopressin
D004075:Diglycerides; D007295:Inositol Phosphates; D019269:Phosphatidylinositol 4,5-Diphosphate; D010716:Phosphatidylinositols; D011518:Proto-Oncogene Proteins; D016760:Proto-Oncogene Proteins c-fos; D011945:Receptors, Angiotensin; D017483:Receptors, Vasopressin; D001127:Arginine Vasopressin; D015240:Phorbol 12,13-Dibutyrate; C028884:1-(beta-mercapto-beta,beta-cyclopentamethylenepropionic acid)-2-(O-ethyl-Tyr)-4-Val-arginine vasopressin; D015544:Inositol 1,4,5-Trisphosphate; D011493:Protein Kinase C; D003894:Deamino Arginine Vasopressin; D002118:Calcium