Neurofilament protein abnormalities in PC12 cells: comparison with neurofilament proteins of normal cultured rat sympathetic neurons

The studies described here characterize abnormalities in the expression of neurofilament (NF) proteins in a clonal rat pheochromocytoma (PC12) cell line as compared with normal NF proteins in cultured rat sympathetic neurons (RSNs). Cytoskeletal extracts from PC12 cells grown in the presence (PC12+ cells) or absence (PC12- cells) of nerve growth factor (NGF) and from RSNs grown in the presence of NGF were analyzed in nitrocellulose replicas of one- and two-dimensional polyacrylamide gels by the immunoblot method using monoclonal antibodies and antiserum to individual NF subunits. RSNs failed to express the high molecular weight NF subunit (NF200) for the first 10 days in culture although both lower molecular weight NF subunits (NF68 and NF150) were expressed by these cells. At later times in culture, all three NF subunits were present in immunoblots of RSNs. The immunoblot profile of NF proteins in PC12- cells was identical to that of RSNs grown in culture for up to 10 days. Growth of PC12 cells in NGF for up to 3 weeks did not alter this immunoblot profile except that no immunoband corresponding in NF200 was seen and the immunobands corresponding to NF68 and NF150 became more prominent. These data suggest that abnormalities in NF protein expression in PC12 cells are due to a paucity of NF200 or to the presence of immunochemically altered NF200. PC12 cells are an attractive model system for probing abnormal NF metabolism.