Integrins
Cell adhesion is a basic process in cell biology, controlling cell growth, death, differentiation, movement, and tissue organization in normal cells, as well as the proliferation and metastasis of tumor cells. A major family of cell adhesion receptors is the integrins [see family, ligands]. Several of the integrins (then called VLA proteins) were initially discovered and functionally characterized in my laboratory, between 1982-1990. At present, we continue to study integrins, with a particular focus on the laminin-binding integrins (α3β1, α6β1, α6β4) on tumor cells and the α4β1 integrin on leukocytes. To a greater extent than many other integrins, these particular integrins assemble into functionally important complexes with other transmembrane proteins, such as tetraspanin proteins. Studies of these lateral associations represent an exciting new dimension in our appreciation of cell adhesion mechanisms.

Tetraspanins
Tetraspanin functions, key domains, role in cancer, and integrin association properties have been reviewed. The tetraspanin protein family has many members (32 in mammals, 35 or more in Drosophila, 21 in worm). These proteins themselves are not well established as ligands or receptors, but rather, they assemble into functionally important complexes with other transmembrane proteins, and signaling enzymes. Although little is known about most tetraspanins, some key functional insights have emerged. For example, tetraspanins are required during mammalian fertilization, regulate signaling through growth factor receptors (eg. EGF receptor), play key roles in the immune system (particularly at the immune synapse), regulate neuronal-astrocyte interactions in brain, facilitate neuromuscular synapse formation in Drosophila embryos, and regulate integrin dependent cell migration and adhesion-strengthening functions [see 2003 review in Annu Rev Cell Dev Biol].