Transfected human somatostatin receptor type 2, SSTR2, not only inhibits adenylate cyclase but also stimulates phospholipase C and Ca2+ mobilization.
COS-7 cells were transfected with human somatostatin (SRIF) receptor type 1 and 2 (human SSTR1 and SSTR2, respectively) cDNAs. In human SSTR2-expressing cells, SRIF not only inhibited forskolin-induced cAMP accumulation but also stimulated phospholipase C and Ca2+ mobilization. While the inhibition of cAMP accumulation was completely reversed by pertussis toxin (PTX) treatment of the cells, SRIF-induced activation of phospholipase C and Ca2+ mobilization was partially but not completely inhibited by the toxin treatment. In human SSTR1-expressing cells, however, SRIF induced only slight inhibition of cAMP accumulation and stimulation of phospholipase C-Ca2+ system. We conclude that the transfected SSTR2 can couple to phospholipase C as well as adenylate cyclase in a stimulatory and inhibitory manner, respectively. Both PTX-sensitive and -insensitive GTP-binding proteins may be involved in the SSTR2 signal transduction mechanisms.
Tomura
H
H
Department of Physical Biochemistry, Gunma University, Maebashi, Japan.
Okajima
F
F
Akbar
M
M
Abdul Majid
M
M
Sho
K
K
Kondo
Y
Y
D000255:Adenosine Triphosphate / Q000494:pharmacology; D037361:Adenylate Cyclase Toxin; D000067956:Adenylyl Cyclase Inhibitors; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D018076:DNA, Complementary / Q000235:genetics; D019204:GTP-Binding Proteins / Q000378:metabolism; D006801:Humans; D037342:Pertussis Toxin; D017481:Receptors, Somatostatin / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D013004:Somatostatin / Q000378:metabolism / Q000494:pharmacology; D014162:Transfection; D010738:Type C Phospholipases / Q000378:metabolism*; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D037361:Adenylate Cyclase Toxin; D000067956:Adenylyl Cyclase Inhibitors; D018076:DNA, Complementary; D017481:Receptors, Somatostatin; D010566:Virulence Factors, Bordetella; D013004:Somatostatin; D000255:Adenosine Triphosphate; D037342:Pertussis Toxin; D010738:Type C Phospholipases; D019204:GTP-Binding Proteins; D002118:Calcium