Accumulation of 210 kDa microtubule-interacting protein in differentiating P19 embryonal carcinoma cells.

The MA-01 antigen, a thermolabile 210 kDa microtubule-interacting protein, is present in P19 embryonal carcinoma cells on microtubular structures as well as in cytosol. After aggregation of the cells and subsequent incubation with all-trans-retinoic acid (RA), the level of MA-01 expression increased approximately 10 times during 15 days. The increase started after 2 days of incubation with RA and preceded the appearance of neuron-specific tubulin betaIII, MAP2C and neurofilaments. Such elevated expression of MA-01 antigen was not detected in P19 cells treated with dimethylsulfoxide. These data indicate that enhanced expression of MA-01 antigen is one of the earliest events occurring in P19 cells during neuronal differentiation.