Absence of TrkB and Insulin receptor beta in the Triton insoluble low-density fraction (raft)

Cholesterol- and glycolipid-enriched microdomains within the plasma membran e of animal cells, including neurons, have been purified and used as a low- density membrane domain after extraction with Triton X-100 (raft), or after subcellular fractionation without detergent (LDM). In this study, we compa red the protein compositions in the raft and the LDM. Membrane receptors, a cylated- and glycosylphosphatidylinositol (GPI)- anchored proteins were enr iched in the LDM. Further treatment of the LDM with Triton X-100 excluded t he membrane receptors, TrkBs and insulin receptor beta. In the presence of calcium ions, the endogenous tyrosine kinase activities in the LDM and the raft were enhanced, suggesting an important role of calcium ions in the sig nal transduction via the LDM and the raft. NeuroReport 11:1307-1311 (C) 200 0 Lippincott Williams & Wilkins.