The Role of Protein Kinase C as a Regulator of NG115‐401L Neuronal Cell Calcium Signaling Pathways

Abstract

The molecular regulation of non-voltage gated calcium influx continues to be an important but poorly characterized signaling pathway in cellular physiology. We have previously characterized unique features of calcium influx in the NG115-401L (401L) neuronal cell line, revealing a phenotype that appears to depend on a conformational coupling mode for the regulation of both calcium influx and release. In this study, we used ratiometric microscope photometry on Fura 2 loaded 401L cells to further probe the apparatus mediating calcium influx when cells are stimulated with pro-inflammatory hormones such as bradykinin. In particular, we have examined the effects of pharmacological modulation of protein kinase C (PKC) on native 401L cells and on cells overexpressing canonical transient receptor potential (TRPC) ion channels. Our preliminary results reveal that inhibitors of PKC augment calcium influx in 401L cells suggesting that PKC activation serves to suppresses the calcium influx mechanism. In contrast, pharmacological activation of PKC using phorbol ester treatment did not significantly influence calcium influx in both native or TRPC overexpressing 401L cells. Intriguingly, we observed that PKC activation in the presence of extracellular calcium elicited discharge from intracellular calcium stores, suggesting a composite target containing PKC activity regulating both calcium release and influx. This work was supported by a grant from the National Institutes of Neurological Disorders and Stroke (1R15 NS048041-01A1) to D.W.T.