Author(s): Hukovic N, Panetta R, Kumar U, Patel YC
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Abstract Agonist regulation of somatostatin receptors (SSTRs) was investigated in stable CHO-K1 cells individually expressing the 5 human (h) SSTR subtypes. hSSTR 2,3,4, and 5 displayed rapid agonist-dependent internalization of [125I] LTT SST-28 ligand in a time- and temperature-dependent manner over 60 min. Maximum internalization of radioligand occurred with hSSTR3 (78\%) followed by hSSTR5 (66\%), hSSTR4 (29\%) and hSSTR2 (20\%). In contrast, hSSTR1 displayed virtually no internalization. Prolonged agonist treatment led to differential upregulation of some of the SSTRs. After 22 h, hSSTR1 was upregulated at the membrane by 110\%, hSSTR2 and hSSTR4 by 26\% and 22\% respectively, whereas hSSTR3 and hSSTR5 showed little change. Agonist-induced recruitment of hSSTR1 to the membrane was confirmed by immunocytochemistry with hSSTR1 antibodies. These results show that SST regulates all 5 hSSTRs by differential subtype selective internalization or upregulation. Subtype selectivity for internalization and upregulation is inversely related.
This article was published in Endocrinology
and referenced in Journal of Pharmacogenomics & Pharmacoproteomics