MIP
Domain
Aquaporins contain two tandem repeats each containing three membrane-spanning domains and a pore-forming loop with the signature motif Asn-Pro-Ala (NPA).
Function
Aquaporins form homotetrameric transmembrane channels, with each monomer independently mediating water transport across the plasma membrane along its osmotic gradient (PubMed:11001937, PubMed:24120416). Specifically expressed in lens fiber cells, this aquaporin is crucial for maintaining lens water homeostasis and transparency. Beyond water permeability, it also acts as a cell-to-cell adhesion molecule, forming thin junctions between lens fiber cells that are essential for maintaining the ordered structure and transparency of the lens (PubMed:24120416).
Involvement in disease
Cataract 15, multiple types
CTRCT15
An opacification of the crystalline lens of the eye that frequently results in visual impairment or blindness. Opacities vary in morphology, are often confined to a portion of the lens, and may be static or progressive. CTRCT15 includes polymorphic, progressive punctate lamellar, cortical, anterior and posterior polar, nonprogressive lamellar with sutural opacities, embryonic nuclear, and pulverulent cortical, among others.
None
The disease is caused by variants affecting the gene represented in this entry.
Post-translational modifications
Subject to partial proteolytic cleavage in the eye lens core. Partial proteolysis promotes interactions between tetramers from adjoining membranes.
Fatty acylated at Met-1 and Lys-238. The acyl modifications, in decreasing order of ion abundance, are: oleoyl (C18:1) > palmitoyl (C16:0) > stearoyl (C18:0) > eicosenoyl (C20:1) > dihomo-gamma-linolenoyl (C20:3) > palmitoleoyl (C16:1) > eicosadienoyl (C20:2).
Sequence Similarities
Belongs to the MIP/aquaporin (TC 1.A.8) family.
Tissue Specificity
Expressed in the cortex and nucleus of the retina lens (at protein level) (PubMed:30790544). Major component of lens fiber gap junctions (PubMed:24120416).
Cellular localization
- Cell membrane
- Multi-pass membrane protein
- Cell junction
- Localizes to thin cell-cell junctions in lens fiber cells.
Alternative names
AQP0, MIP, Lens fiber major intrinsic protein, Aquaporin-0, MIP26, MP26