Transmembrane-4-superfamily proteins CD151 and CD81 associate with α3β1 integrin, and selectively contribute to α3β1-dependent neurite outgrowth

Abstract

Proteins in the transmembrane-4-superfamily (TM4SF) form many different complexes with proteins in the integrin family, but the functional utility of these complexes has not yet been demonstrated. Here we show that TM4SF proteins CD151, CD81, and CD63 co-distribute with α3β1 integrin on neurites and growth cones of human NT2N cells. Also, stable CD151-α3β1 and CD81-α3β1 complexes were recovered in NT2N detergent lysates. Total NT2N neurite outgrowth on laminin-5 (a ligand for α3β1 integrin) was strongly inhibited by anti-CD151 and -CD81 antibodies either together (~ 85% inhibition) or alone (~ 45% inhibition). Notably, these antibodies had no inhibitory effect on NT2N neurites formed on laminin-1 or fibronectin, when α3β1 integrin was not engaged. Neurite number, length, and rate of extension were all affected by anti-TM4SF antibodies. In summary: (1) these substrate-dependent inhibition results strongly suggest that CD151 and CD81 associations with α3β1 are functionally relevant, (2) TM4SF proteins CD151 and CD81 make a strong positive contribution toward neurite number, length, and rate of outgrowth, and (3) NT2N cells, a well-established model of immature central nervous system neurons, can be a powerful system for studies of integrin function in neurite outgrowth and growth cone motility.