The membrane protein A5, a putative neuronal recognition molecule, promotes neurite outgrowth.

The A5 is an unique membrane protein that is expressed in the neurons of the visual system and general somatic sensory system of Xenopus laevis. We cultured retinal explants or trigeminal ganglion neurons on the monolayers of A5-expressing line cells obtained by transfection with the cDNA, and found that the A5-expressing transfectants promote neurite outgrowth for these A5-expressing neurons. The neurite outgrowth-promoting effect was inhibited by anti-A5 antibodies. While, the neurite outgrowth-promotion by the A5 transfectants was not observed for the vestibulocochlear ganglion neurons which lack the A5. These results indicate that the membrane protein A5 is a potent substrate for neurite extension of the A5-expressing neurons but not for the A5-negative ones, suggesting its involvement in specific neuronal interaction.