Dynamic recruitment of phospholipase Cγ 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 Gαi2 and Lyn via protein–protein and raft interactions. Lyn is activated probably by the Gαi2 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-PLCγ2 and CD59 clusters revealed that PLCγ2 molecules are transiently (median = 0.25 s) recruited from the cytoplasm exclusively at the CD59 clusters undergoing STALL, producing the IP3–Ca2+ 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 IP3–Ca2+ signal, via PLCγ2 recruitment. The prolonged, analogue, bulk IP3–Ca2+ signal, which lasts for more than several minutes, is likely generated by the sum of the short-lived, digital-like IP3 bursts, each created by the transient recruitment of PLCγ2 molecules to STALLed CD59.