Functional evidence for presence of lipid rafts in erythrocyte membranes: Gsα in rafts is essential for signal transduction

Abstract

Membrane microdomains enriched in cholesterol and sphingolipids and containing specific membrane proteins are designated as lipid rafts. Lipid rafts have been implicated in cell signaling pathways in various cell types. Heterotrimeric guanine nucleotide-binding protein (Gsa) has been shown to be a raft component of erythrocytes and has been implicated in cell signaling. Rafts are isolated as detergent-resistant microdomains (DRMs) for biochemical analysis. Cholesterol depletion is widely used to disrupt raft structures to study their function in biological membranes. In the present study, we developed an alternate strategy for disrupting raft structures without altering membrane cholesterol content. Lidocaine hydrochloride, an amphipathic local anesthetic, is shown to reversibly disrupt rafts in erythrocyte membranes and alter the Gsa dependent signal transduction pathway. These findings provide evidence for the presence of rafts while maintaining normal cholesterol content in erythrocyte membranes and confirm a role for raft-associated Gsa in signal transduction in erythrocytes. Am. J. Hematol. 83:371-375, 2008. V

Palmitoylation of MPP1 (Membrane-palmitoylated Protein 1)/p55 Is Crucial for Lateral Membrane Organization in Erythroid Cells

“…Moreover, the inhibition of palmitoylation by 2-BrP treatment blocked adducin (a protein of ϳ90 kDa) phosphorylation in response to the G␣ s -mediated stimulation of PKA (supplemental Fig. S4D), which is known to be a palmitoylation and raft-dependent signaling pathway (37).…”

Lipid Rafts Alter the Stability and Activity of the Cholera Toxin A1 Subunit

“…Moreover, the gain of structure for disordered CTA1 is a raft-specific event. Because G s ␣ is present in lipid rafts (23)(24)(25)(26), CTA1 would benefit from the chaperonelike function of lipid rafts upon contact with its G protein target. The resulting gain of structure confers a basal level of activity to CTA1 without acting through allostery because no gain of function was recorded for CTA1 treated with lipid rafts at 25°C.…”

“…G s ␣ is found in lipid rafts at the cytosolic face of the plasma membrane (23)(24)(25)(26). CTA1 would therefore encounter a lipid raft environment upon contact with its G s ␣ target.…”

Sphingomyelinase Treatment on Human Erythrocytes: Influenceon Membrane Lipid Rafts and Malaria Parasite Invasion

“…shown that the presence of Gs in the lipid rafts is essential for the Gs -mediated signal transduction 15) .…”