Agonist-dependent regulation of cloned human somatostatin receptor types 1-5 (hSSTR1-5): subtype selective internalization or upregulation

Endocrinology. 1996 Sep;137(9):4046-9. doi: 10.1210/endo.137.9.8756582.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Biological Transport
  • CHO Cells
  • Cell Membrane / metabolism
  • Cricetinae
  • Humans
  • Immunohistochemistry
  • Receptors, Somatostatin / agonists*
  • Receptors, Somatostatin / metabolism*
  • Temperature
  • Time Factors
  • Up-Regulation*


  • Receptors, Somatostatin