– TPM4, also known as tropomyosin 4, is a member of the tropomyosin family. Members of this family are actin-binding proteins involved in the contractile system of striated and smooth muscles and the cytoskeleton of non-muscle cells. TPM4 is expressed in cardiac tissue and platelets. It is highly expressed in the platelets of hypertensive patients. TPM4 plays a central role, in association with the troponin complex, in the calcium-dependent regulation of vertebrate striated muscle contraction. Smooth muscle contraction is regulated by interaction with caldesmon. In non-muscle cells, it is implicated in stabilizing cytoskeleton actin filaments.