Regulation of neuritogenesis and synaptic transmission by msec7-1, a guanine nucleotide exchange factor, in cultured Aplysia neurons.

msec7-1, a mammalian homologue of yeast sec7p, is known as a GDP/GTP exchange factor (GEF) for the ADP ribosylation factor (ARF) family of small GTPases. Here, we report that msec7-1 overexpression in cultured Aplysia neurons leads to an extensive neuritogenesis in a GEF activity-dependent manner through the modulation of the actin cytoskeleton. Similarly, the overexpression of ARNO, another mammalin GEF, produces extensive neuritogenesis in Aplysia neurons. In addition, msec7-1 overexpression increases the number of varicosities with an altered size and shape in a GEF activity-dependent manner. The overexpression of msec7-1 in pre-synaptic sensory neurons co-cultured with post-synaptic target motor neurons leads to an increase in the amplitude of the excitatory post-synaptic potential through its GEF activity. Our results demonstrate that msec7-1 regulates neuritogenesis and synaptic transmission.