GM1 in the nuclear membrane, previously shown to be up-regulated during neurite outgrowth, has been found to influence nuclear Ca2+ flux during differentiation of Neuro-2a cells. Nuclei were isolated from cultured Neuro-2a cells before and after neuraminidase-induced neuritogenesis and incubated with 45Ca2+ for varying periods to determine uptake/efflux of Ca2+. At 5, 10, and 15 min 45Ca2+ levels in nuclei from differentiated cells were significantly lower than those in nuclei from untreated cells. The same result was obtained when the GM1 level was elevated artificially by preincubation of the nuclei in 10 microM GM1. In experiments designed to measure efflux specifically, isolated nuclei preincubated in GM1 released 45Ca2+ more rapidly than untreated nuclei. We conclude that one role of GM1 in the nuclear membrane is to alter Ca2+ regulatory mechanisms in the nucleus following onset of neuronal process outgrowth.