Journal
CELLULAR SIGNALLING
Volume 20, Issue 2, Pages 400-408Publisher
ELSEVIER SCIENCE INC
DOI: 10.1016/j.cellsig.2007.10.029
Keywords
RGK; GTP; GTPase; Rem2; VDCC; Ca-v beta; phosphatidylinositol
Categories
Funding
- NCRR NIH HHS [P20 RR20171, P20 RR020171] Funding Source: Medline
- NHLBI NIH HHS [R56 HL074091, R01 HL072936-04, HL072936, T32 HL072743, R01 HL072936, HL074091, R01 HL074091] Funding Source: Medline
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Voltage dependant calcium channels (VDCC) play a critical role in coupling electrical excitability to important physiological events such as secretion by neuronal and endocrine cells. Rem2, a GTPase restricted to neuroendocrine cell types, regulates VDCC activity by a mechanism that involves interaction with the VDCC beta subunit (Cav beta). Mapping studies reveal that Rem2 binds to the guanylate kinase domain (GK) of the Cav beta subunit that also contains the high affinity binding site for the pore forming and voltage sensing VDCC a subunit (Ca-v beta) interaction domain (AID). Moreover, fine mapping indicates that Rem2 binds to the GK domain in a region distinct from the AID interaction site, and competitive inhibition studies reveal that Rem2 does not disrupt Ca-v alpha - Ca-v beta binding. Instead, the Cav beta subunit appears to serve a scaffolding function, simultaneously binding both Rem2 and AID. Previous studies have found that in addition to Ca-v beta binding, Rem2 must be localized to the plasma membrane to inhibit VDCC function. Plasma membrane localization requires the C-tenninus of Rem2 and binding studies indicate that this domain directs phosphorylated phosphatidylinositide (PIP) lipids association. Plasma membrane localization may provide a unique point of regulation since the ability of Rem2 to bind PIP lipids is inhibited by the phosphoserine dependant binding of 14-3-3 proteins. Thus, in addition to Ca-v beta binding, VDCC blockade by Rem2 is likely to be controlled by both the localized concentration of membrane PIP lipids and direct 14-3-3 binding to the Rem2 C-terminus. (C) 2007 Elsevier Inc. All rights reserved.
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