Cross-reactivity of an antineurofilament antibody with a troponin-T isoform

Histochemical examination has revealed that a monoclonal antibody raised against the 200-kilodalton (kd) subunit of neurofilament reacts not only with neural tissue but with type 1 and type 2C fibers of skeletal muscle. To identify the cross-reactive substance(s), rat soleus muscle, which includes type 1 and type 2C fibers, was separated into a soluble fraction and an insoluble myofibrillar fraction. Western blot analysis demonstrated that the antibody reacted with 30-kd and 36-kd polypeptides in the soluble fraction and with a 38-kd polypeptide in the insoluble fraction. We isolated a fraction that contained the 38-kd polypeptide from the insoluble fraction. The material in this fraction bound to F-actin. Two-dimensional electrophoresis of the fraction showed that the 38-kd polypeptide was part of the group of isoforms of troponin-T, which was identified by a monoclonal antibody developed against troponin-T. Thus, we conclude that this antineurofilament antibody recognizes one of the isoforms of troponin-T in type 1 and type 2C fibers.