An increase in store‐operated channel activity occurs during differentiation of hippocampal neurons

During differentiation of hippocampal H19‐7 cells, TRPC1 and TRPC3 protein levels are up‐regulated, and TRPC4 and TRPC7 protein levels are down regulated (1). Immunostaining studies show that a dramatic up‐regulation of TRPC1 protein levels also occurs during the in vitro differentiation of primary hippocampal neurons. More recent studies in H19‐7 cells show that expression levels of TRPC5 are down‐regulated, and those of TRPC6 are up‐regulated, during neuronal differentiation. Store‐operated currents in H19‐7 cells were monitored in whole‐cell patch clamp mode, and currents were found to be lower in hippocampal precursor cells than in differentiated hippocampal neurons [0.31 ± 0.04 (n=9) pA/pF versus 1.6 ± 0.2 (n=11) pA/pF] . When the holding potential of differentiated H19‐7 cells was shifted from −60 mV to 0 mV, the activated current rapidly increased to 6 pA/pF, indicating that the current is inactivated at negative holding potentials, as is seen for I CRAC currents. However, the I‐V curves for the up‐regulated currents indicate that they are mediated by an I SOC subtype (low Ca 2+ /Na + selectivity), rather than by an I CRAC subtype (high Ca 2+ /Na + selectivity), of store‐operated channel. This work was supported by National Institute of General Medical Sciences grant GM54500 to M.L.V.