Non-muscle myosin heavy chain as a possible target for protein encoded by metastasis-related mts-1 gene

The mts-1 gene is associated with the expression of the metastatic phenotype of tumor cells. The protein product of the mts-1 gene belongs to the S100 family of Ca(2+)-binding proteins with unknown biochemical function. In the present work, monoclonal anti-Mts-1 antibodies were used to isolate and characterize Mts-1 protein possible targets. Mts-1 protein can be immunoprecipitated by both anti-Mts-1 and anti-myosin antibodies as a complex with myosin from lysates of different mouse and human cell lines. Precipitation of myosin by anti-Mts-1 antibodies is specific and depends on the presence of Mts-1 protein. Ca(2+)-dependent association between Mts-1 protein and the heavy chain of non-muscle myosin was demonstrated by blot overlay technique. Furthermore, association between myosin and Mts-1 was confirmed by sucrose gradient analysis. Finally, immunofluorescent staining of the mouse mammary adenocarcinoma cell line showed that Mts-1 protein is co-localized with the myosin complex. The data suggest that the target for Mts-1 protein is a heavy chain of non-muscle myosin.