Association of heat shock proteins and neuronal membrane components with lipid rafts from the rat brain.

Lipid rafts are specialized plasma membrane microdomains enriched in cholesterol and sphingolipids that serve as major assembly and sorting platforms for signal transduction complexes. Constitutively expressed heat shock proteins Hsp90, Hsc70, Hsp60, and Hsp40 and a range of neurotransmitter receptors are present in lipid rafts isolated from rat forebrain and cerebellum. Depletion of cholesterol dissociates these proteins from lipid rafts. After hyperthermic stress, flotillin-1, a lipid raft marker protein, does not show major change in levels. Stress-inducible Hsp70 is detected in lipid rafts at 1 hr posthyperthermia, with the peak levels attained at 24 hr, suggesting that Hsp70 may play roles in maintaining the stability of lipid raft-associated signal transduction complexes following neural stress.