GPI-anchored receptor clusters transiently recruit Lyn and Gα for temporary cluster immobilization and Lyn activation: single-molecule tracking study 1

Abstract

The signaling mechanisms for glycosylphosphatidylinositol-anchored receptors (GPI-ARs) have been investigated by tracking single molecules in living cells. Upon the engagement or colloidal gold–induced cross-linking of CD59 (and other GPI-ARs) at physiological levels, CD59 clusters containing three to nine CD59 molecules were formed, and single molecules of Gαi2 or Lyn (GFP conjugates) exhibited the frequent but transient (133 and 200 ms, respectively) recruitment to CD59 clusters, via both protein–protein and lipid–lipid (raft) interactions. Each CD59 cluster undergoes alternating periods of actin-dependent temporary immobilization (0.57-s lifetime; stimulation-induced temporary arrest of lateral diffusion [STALL], inducing IP3 production) and slow diffusion (1.2 s). STALL of a CD59 cluster was induced right after the recruitment of Gαi2. Because both Gαi2 and Lyn are required for the STALL, and because Lyn is constitutively recruited to CD59 clusters, the STALL of CD59 clusters is likely induced by the Gαi2 binding to, and its subsequent activation of, Lyn within the same CD59 cluster.

The coreceptor CD2 uses plasma membrane microdomains to transduce signals in T cells

“…Actin polymerization appears to be important in the initial formation of the microdomains but is not essential for their continued stability. It has been suggested that these microdomains are primarily held together by networks of protein interactions (Douglass and Vale, 2005), although lipid rafts (phase-partitioned lipids) could play important roles as well (Harder, 2004;Suzuki et al, 2007). Other membrane proteins in the T cell as well as in other immune cells also have been reported to segregate into various domain structures (Dustin et al, 1998;Bromley et al, 2001;Davis and Dustin, 2004;Kaizuka et al, 2007).…”

Order of lipid phases in model and plasma membranes

“…A tenet of the model is that small, dynamic cholesterol-sphingolipid-enriched assemblies can be induced to coalesce into larger, more stable structures through clustering of domain components (2). Although experimental data support cholesterol-dependent nano-scale membrane heterogeneity (3)(4)(5)(6)(7)(8) and selective domain formation upon raft cross-linking (9)(10)(11)(12), the mechanisms that govern such associations in cell membranes remain unclear.…”

The differential protein and lipid compositions of noncaveolar lipid microdomains and caveolae

“…Each nanocluster produces a signal in a way of quantized burst, so the cell can easily modulate the timing and amplitude of the signal simply by synchronizing the quantity of these nanoclusters [34,35]. Our results with caveolin-1 knockdown 3T3-L1 cells indicate that lipid rafts are the signal platform for the IGF-1 receptor [5].…”

“…Compared with the stable caveolae, the short-lived unstable nanoscale clusters are more efficient for signal transduction [34][35][36]. Each nanocluster produces a signal in a way of quantized burst, so the cell can easily modulate the timing and amplitude of the signal simply by synchronizing the quantity of these nanoclusters [34,35].…”