Mechanisms of desensitization and resensitization of proteinase- activated receptor-2

Stephan K. Böhm, Lev M. Khitin, Eileen F. Grady, Gregory Aponte, Donald G. Payan, Nigel W. Bunnett

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Proteinase-activated receptor-2 (PAR-2) is a G-protein-coupled receptor that is expressed by intestinal epithelial cells, which are episodically exposed to pancreatic trypsin in the intestinal lumen. Trypsin cleaves PAR-2 to expose a tethered ligand, which irreversibly activates the receptor. Thus, PAR-2 may desensitize and resensitize by novel mechanisms. We examined these mechanisms in kidney epithelial cells, stably expressing human PAR-2, and intestinal epithelial cells, which naturally express PAR-2. Trypsin stimulated a prompt increase in [Ca2+](i), due to mobilization of intracellular Ca2+, followed by a sustained plateau, due to influx of extracellular Ca2+. Repeated application of trypsin caused marked desensitization of this response, which is due in part to (a) irreversible cleavage of the receptor by trypsin and (b) protein kinase C-mediated termination of signaling. Trypsin exposure resulted in internalization of PAR-2 into early endosomes and then lysosomes; but endocytosis was not the mechanism of rapid desensitization. Thus, activated PAR-2 is endocytosed and degraded. The Ca2+ response to trypsin resensitized by 60-90 min. Brefeldin A, which disrupted Golgi stores of PAR-2, and cycloheximide, which inhibited protein synthesis, markedly attenuated resensitization. Thus, PAR-2-mediated Ca2+ mobilization desensitizes by irreversible receptor cleavage, protein kinase C-mediated termination of signaling, and PAR-2 targeting to lysosomes. It resensitizes by mobilization of large Golgi stores and synthesis of new receptors.

Original languageEnglish (US)
Pages (from-to)22003-22016
Number of pages14
JournalJournal of Biological Chemistry
Issue number36
StatePublished - 1996

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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