Secretogranin I/chromogranin B is a heparin-binding adhesive protein

The major heparin-binding protein secreted by PC12 cells was purified from conditioned medium. Amino-terminal sequencing of the purified protein identified it as secretogranin I/chromogranin B (SgI/ChmB). The protein showed the same electrophoretic mobility and biochemical characteristics as previously reported for SgI/ChmB and could be purified in high yield using a simple procedure. In vitro experiments demonstrated that SgI/ChmB effectively promoted cell-substratum adhesion of NIH 3T3 and PC12 cells and supported neurite outgrowth in primary hippocampal neurons. Thus, SgI/ChmB may be a new member of the family of heparin-binding extracellular matrix proteins that mediate cell adhesion and support neurite outgrowth.