Calcium-sensing Receptor-mediated ERK1/2 Activation Requires Gαi2 Coupling and Dynamin-independent Receptor Internalization

• Published in: The Journal of biological chemistry Vol. 279; no. 11; pp. 10060 - 10069
• Main Authors: Holstein, Deborah M., Berg, Kelly A., Leeb-Lundberg, L.M. Fredrik, Olson, Merle S., Saunders, Christine
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 12.03.2004
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M312039200

The calcium-sensing receptor (CaR) recently has been shown to activate MAP kinase (ERK1/2) in various cell types as well as in heterologous expression systems. In this study we show that the CaR agonist NPS R-467 (1 μm), which does not activate the CaR by itself, robustly activates ERK1/2 in the presence of a low concentration of Ca2+ (0.5 mm CaCl2) in human embryonic kidney (HEK) cells permanently expressing the human CaR (HEK-hCaR). Ca2+ (4 mm) also activates ERK1/2 but with differing kinetics. CaR-dependent ERK1/2 activation begins to desensitize to 4 mm Ca2+ after 10 min, whereas there is no desensitization to NPS R-467/CaCl2 as late as 4 h. Moreover, recovery from desensitization occurs as rapidly as 30 min with 4 mm CaCl2. Pretreatment of HEK-hCaR cells with concanavalin A (250 μg/ml) to block CaR internalization completely eliminated the NPS R-467/CaCl2-mediated ERK1/2 activation but did not block the 2-min time point of 4 mm Ca2+-mediated ERK1/2 activation. Neither dominant-negative dynamin (K44A) nor dominant-negative β-arrestin inhibited ERK1/2 activation by either CaR agonist treatment, suggesting that CaR-elicited ERK1/2 signaling occurs via a dynamin-independent pathway. Pertussis toxin pretreatment partially attenuated the 4 mm Ca2+-ERK1/2 activation; this attenuated activity was completely restored by co-expression of the Gαi2C351I but not Gαi1C351I or Gαi3C351I G proteins, PTX-insensitive G protein mutants. Taken together, these data suggest that both 4 mm Ca2+ and NPS R-467/CaCl2 activate ERK1/2 via distinguishable pathways in HEK-hCaR cells and may represent a nexus to differentially regulate differentiation versus proliferation via CaR activation.