The somatostatin receptor SSTR1 is coupled to phosphotyrosine phosphatase activity in CHO-K1 cells.

TitleThe somatostatin receptor SSTR1 is coupled to phosphotyrosine phosphatase activity in CHO-K1 cells.
Publication TypeJournal Article
Year of Publication1994
AuthorsFlorio T, Rim C, Hershberger RE, Loda M, Stork PJ
JournalMol Endocrinol
Date Published1994 Oct
KeywordsAdenylate Cyclase Toxin, Animals, CHO Cells, Cloning, Molecular, Cricetinae, DNA, Complementary, Enzyme Activation, Gene Transfer Techniques, Pertussis Toxin, Protein Tyrosine Phosphatases, Rats, Receptors, Somatostatin, Recombinant Proteins, Somatostatin, Virulence Factors, Bordetella

Somatostatin receptors are abundantly expressed on a variety of human endocrine and epithelial tumors. The ability of these receptors to couple to effector pathways that inhibit the growth of these tumor cells has prompted the use of somatostatin agonists in the treatment of human neoplasms. It has been demonstrated that somatostatin stimulates a phosphotyrosine phosphatase in human tumor cells through a receptor-mediated process. This stimulation may counteract the growth-promoting properties of growth factors and the receptor tyrosine kinases that they activate. The recent cloning and characterization of distinct somatostatin receptor subtypes raise the possibility that different receptor subtypes mediate distinct effector pathways. To determine whether cloned somatostatin receptors could mediate coupling to phosphotyrosine phosphotyrosine phosphatase activity, we examined phosphatase activity after somatotostatin activation of the rat somatostatin receptors SSTR1 and SSTR2 after their stable expression in heterologous Chinese Hamster Ovary (CHO-K1) cells. We found that stimulation of SSTR1 cells was capable of increasing phosphotyrosine phosphatase activity, despite the coupling of both receptors to the inhibition of adenylyl cyclase in these cells. This activation was characterized by an EC50 of 70 nM and was sensitive to pertussis toxin. In addition, we demonstrate that activation of phosphotyrosine phosphatase activity in pituitary cell lines correlates with the endogenous expression of the SSTR1 gene within these cells.

Alternate JournalMol Endocrinol
PubMed ID7854346
Grant List1RO1 DK-45921 / DK / NIDDK NIH HHS / United States
Related Faculty: 
Massimo Loda, M.D.

Pathology & Laboratory Medicine 1300 York Avenue New York, NY 10065 Phone: (212) 746-6464
Surgical Pathology: (212) 746-2700