Neuronal adhesion molecule telencephalin induces rapid cell spreading of microglia.

Telencephalin (TLCN) is a neuronal surface glycoprotein whose expression is restricted to the telencephalon, the most rostral segment of the brain. TLCN binds to lymphocyte function-associated antigen-1 (LFA-1) integrin. In the central nervous system, LFA-1 is selectively and constitutively expressed by microglia, suggesting that TLCN/LFA-1 binding may mediate cell-cell interactions between telencephalic neurons and microglia. In the present study, we investigated the effects of recombinant TLCN protein on the morphology of microglia. TLCN induced an intensive spreading of lamellipodia, causing a rapid change in microglial morphology. In contrast, TLCN induced no significant change in morphology of neuroblastoma and fibroblasts. Furthermore, the TLCN-induced spreading of microglia was accompanied by a clustering of LFA-1 on cell surface membrane. These results provide evidence that TLCN binding to the surface of microglia transduces signals into microglia that mediate or accelerate cell spreading and LFA-1 redistribution, implying that neuronal TLCN may control the state and/or function of microglia in both physiological and pathological conditions.