COMMENTARY 4143 Complexes of tetraspanins with integrins: more than meets the eye Fedor Berditchevski CRC Institute for Cancer Studies, The University of Birmingham, Edgbaston, Birmingham, B15 2TA, UK Author for correspondence (e-mail:
[email protected]) Journal of Cell Science 114, 4143-4151 (2001) © The Company of Biologists Ltd Summary The transmembrane proteins of the tetraspanin membrane, integrin-tetraspanin signalling complexes superfamily are implicated in a diverse range of biological are partitioned into specific microdomains proximal to phenomena, including cell motility, metastasis, cell cholesterol-rich lipid rafts. A substantial fraction of proliferation and differentiation. The tetraspanins are tetraspanins colocalise with integrins in various associated with adhesion receptors of the integrin family intracellular vesicular compartments. It is proposed that and regulate integrin-dependent cell migration. In cells tetraspanins can influence cell migration by one of the attached to the extracellular matrix, the integrin- following mechanisms: (1) modulation of integrin tetraspanin adhesion complexes are clustered into a distinct signalling; (2) compartmentalisation of integrins on the cell type of adhesion structure at the cell periphery. Various surface; or (3) direction of intracellular trafficking and tetraspanins are associated with phosphatidylinositol 4- recycling of integrins. kinase and protein kinase C isoforms, and they may facilitate assembly of signalling complexes by tethering these enzymes to integrin heterodimers. At the plasma Key words: Tetraspanin, Integrin, Migration, Signalling Introduction relatively well conserved among tetraspanins (Fig. 1). A Tetraspanins (also referred to as tetraspans or TM4SF proteins) combination of all the above features distinguishes tetraspanins are a family of widely expressed four-transmembrane-domain from a diverse group of proteins that have four transmembrane proteins.