In the context of this review it is important to mention another cholesterol and ganglioside enriched membrane domain, which share some similarity but are physically and functionally distinct from the lipid rafts, the tetraspanin-enriched microdomains (TEMs). Tetraspanins are a large family of small membranespanning proteins (Yanez-Mo et al., 2011) , numbering at least 32 family members in mammals. They are involved in a whole range of cellular processes, from cell morphology and motility to signaling pathways (Hemler, 2005) .