Water channel (PubMed:24120416). Channel activity is down-regulated by CALM when cytoplasmic Ca(2+) levels are increased. May be responsible for regulating the osmolarity of the lens. Interactions between homotetramers from adjoining membranes may stabilize cell junctions in the eye lens core (By similarity). Plays a role in cell-to-cell adhesion and facilitates gap junction coupling (PubMed:24120416).
Phosphorylation at one of these sites (serine 243) could be increased by A kinase in vitro. phosphorylation of MIP reconstituted into single bilayers increased the voltage dependence and long-term closures of the channels observed.