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Calcium Influx Becomes More Complex

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Science's STKE  22 Feb 2000:
Vol. 2000, Issue 20, pp. tw8
DOI: 10.1126/stke.2000.20.tw8

Ca2+ influx across the plasma membrane through Ca2+ release activated channels (ICRAC) can occur in nonexcitable cells in response to agonist-induced Ca2+ release from intracellular stores. These ICRAC channels may be activated by a direct mechanical connection to inositol 1,4,5-trisphosphate receptors (IP3R) in nearby organelles. These receptors also bind to phosphatidylinositol 4,5-bisphosphate (PIP2) in the plasma membrane. Kaznacheyeva et al. propose that a functional ICRAC- IP3R- PIP2 complex regulates capacitative Ca2+ influx. The activity of a putative ICRAC channel called Imin was inhibited by PIP2, but was enhanced when the lipid was blocked with an antibody. Antibody treatment increased the ability of IP3 to activate Imin. The authors propose that when phospholipase C is activated, PIP2 that is associated with IP3R is hydrolyzed to form IP3, and a resultant conformational change in the IP3R is coupled to the opening of associated Imin channels.

Kaznacheyeva, E., Zubov, A., Nikolaev, A., Alexeenko, V., Bezprozvanny, I., and Mozhayeva, G.N. (2000) Plasma membrane calcium channels in human carcinoma A431 cells are functionally coupled to inositol 1,4,5-trisphosphate receptor- phosphatidylinositol 4,5-bisphosphate complexes. J. Biol. Chem. 275: 4561-4564. [Abstract] [Full Text]

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