Cooperates with AGTR2 to inhibit ERK2 activation and cell proliferation. May be required for AGTR2 cell surface expression. Together with PTPN6, induces UBE2V2 expression upon angiotensin-II stimulation. Isoform 1 inhibits breast cancer cell proliferation, delays the progression of mitosis by prolonging metaphase and reduces tumor growth. {ECO:0000269|PubMed:12692079, ECO:0000269|PubMed:19794912}. This is the function of Ensembl gene identifier ENSG00000129422 (MTUS1, microtubule associated scaffold protein 1).