||May play a role in tumor progression. Ability to promote tumor growth may be mainly due to repression of apoptosis as opposed to proliferation. Has anti-adhesive properties. Seems to alter cellular behavior through both anti-adhesive effects on cell-cell and cell-extracellular matrix interactions and in its ability to act as an intramembrane ligand for ERBB2. Plays an important role in cell proliferation and differentiation of epithelial cells by inducing specific phosphorylation of ERBB2. In polarized epithelial cells segregates ERBB2 and other ERBB receptors and prevents ERBB2 from acting as a coreceptor. The interaction with ERBB2 leads to enhanced expression of CDKN1B. The formation of a MUC4-ERBB2-ERBB3-NRG1 complex leads to down-regulation of CDKN1B, resulting in repression of apoptosis and stimulation of proliferation. The MUC4-ERBB2 complex causes site-specific phosphorylation of the ERBB2 'Tyr-1248' (By similarity).
||Mucin-4 beta chain: Cell membrane, Multi-pass membrane protein, SUBCELLULAR LOCATION: Mucin-4 alpha chain: Secreted
||Expression is developmentally regulated in the mammary gland, dramatically increases in the lactating gland compared with the virgin mammary gland, while decreasing again during mammary gland involution. Expressed in 13762 ascites cells. Overexpressed in