Dynamic recruitment of phospholipase C gamma at transiently immobilized GPI-anchored receptor clusters induces IP3-Ca2+ signaling: single-molecule tracking study 2.

Clusters of CD59, a glycosylphosphatidylinositol-anchored receptor (GPI-AR), with physiological sizes of approximately six CD59 molecules, recruit Galphai2 and Lyn via protein-protein and raft interactions. Lyn is activated probably by the Galphai2 binding in the same CD59 cluster, inducing the CD59 cluster's binding to F-actin, resulting in its immobilization, termed stimulation-induced temporary arrest of lateral diffusion (STALL; with a 0.57-s lifetime, occurring approximately every 2 s). Simultaneous single-molecule tracking of GFP-PLCgamma2 and CD59 clusters revealed that PLCgamma2 molecules are transiently (median = 0.25 s) recruited from the cytoplasm exclusively at the CD59 clusters undergoing STALL, producing the IP(3)-Ca(2+) signal. Therefore, we propose that the CD59 cluster in STALL may be a key, albeit transient, platform for transducing the extracellular GPI-AR signal to the intracellular IP(3)-Ca(2+) signal, via PLCgamma2 recruitment. The prolonged, analogue, bulk IP(3)-Ca(2+) signal, which lasts for more than several minutes, is likely generated by the sum of the short-lived, digital-like IP(3) bursts, each created by the transient recruitment of PLCgamma2 molecules to STALLed CD59.