NONMUSCLE MYOSIN HEAVY-CHAIN AS A POSSIBLE TARGET FOR PROTEIN ENCODEDBY METASTASIS-RELATED MTS-1 GENE

The mts-1 gene is associated with the expression of the metastatic phe notype of tumor cells. The protein product of the mts-1 gene belongs t o the S100 family of Ca2+-binding proteins with unknown biochemical fu nction. In the present work, monoclonal anti-Mts-1 antibodies were use d to isolate and characterize Mts-1 protein possible targets. Mts-1 pr otein can be immunoprecipitated by both anti-Mts-1 and anti-myosin ant ibodies as a complex with myosin from lysates of different mouse and h uman cell lines. Precipitation of myosin by anti-Mts-1 antibodies is s pecific and depends on the presence of Mts-1 protein. Ca2+-dependent a ssociation between Mts-1 protein and the heavy chain of non-muscle myo sin was demonstrated by blot overlay technique. Furthermore, associati on between myosin and Mts-1 was confirmed by sucrose gradient analysis . Finally, immunofluorescent staining of the mouse mammary adenocarcin oma cell line showed that Mts-1 protein is co-localized with the myosi n complex. The data suggest that the target for Mts-1 protein is a hea vy chain of non-muscle myosin.