S100 beta is a target protein of neurocalcin delta, an abundant isoform in glial cells

To clarify the function of neurocalcin delta, an isoform found abundantly in glial cells, we attempted to find its target proteins by using neurocalcin delta-affinity chromatography and the 125I-neurocalcin delta gel-overlay method. The 10, 14, 27, 36 and 50 kDa bands found on SDS/PAGE bound to 125I-neurocalcin delta, and 10, 11, 19, 24, 26, 50 and 70 kDa proteins were eluted from a neurocalcin delta-affinity column in a Ca(2+)-dependent manner. Sequence analysis of proteolytic peptides revealed the following identities: S100 beta (10 kDa), S100 alpha (11 kDa), myelin basic protein (19 kDa), glyceraldehyde-3-phosphate dehydrogenase (36 kDa) and tubulin beta-chain (50 kDa). A zero-length cross-linking study indicated that 1 mol of S100 beta bound to 1 mol of neurocalcin delta. With the gel-overlay method, purified S100 beta protein and calcyclin bound to 125I-neurocalcin delta whereas calgizarrin and calvasculin, other members of the S100 family, did not. These findings suggest that S100 beta is one of the target proteins of neurocalcin delta, and the neurocalcin delta-S100 beta complex may be involved in Ca(2+)-signalling in the glial cell.