Ca_V2.3 channel and PKCλ: new players in insulin secretion
J. Clin. Invest. Shao-Nian Yang, et al. 115:16 doi:10.1172/JCI23970 [Go to this article.]

Figure 1
The functional Ca_V channel consists of pore-forming subunits Ca_Vα1 and auxiliary subunits Ca_Vβ, Ca_Vα2/δ, and Ca_Vγ. Four types of Ca_Vα₁ subunits, designated Ca_V1.2, Ca_V1.3, Ca_V2.1, and Ca_V2.3, conducting L-, P/Q-, and R-type Ca²⁺ currents, have been identified in the mouse β cell. Glucose-stimulated insulin secretion is characterized by a rapid first phase of insulin release for about 10 minutes, followed by a nadir, and subsequently a gradually increasing second phase reaching a plateau after 25 to 30 minutes (inset). Insulin-containing granules (IG) are functionally divided into three pools: the reserve pool (RP), the readily releasable pool (RRP), and the immediately releasable pool (IRP). The present consensus is that the K_ATP channel–dependent mechanisms trigger first-phase insulin secretion from the IRP by opening Ca_V1.2 and Ca_V1.3 channels. The K_ATP channel–independent mechanisms underlie second-phase insulin secretion by recruiting insulin-containing granules from RP and RRP to IRP. The Ca²⁺ influx through β cell Ca_V2.3 channels is now demonstrated to play a prominent role in second-phase insulin secretion. Ca_V1.2/1.3, Ca_V1.2 channels or Ca_V1.3 channels; Ca_V2.3, Ca_V2.3 channels; Depol, depolarization; GLUT2, glucose transporter 2.