AQP0 Membrane Protein Introduction

Introduction of AQP0

AQP0 is also known as lens fiber major intrinsic protein, MIP26, MP26, Aquaporin-CHIP, Urine water channel, water channel protein for red blood cells and kidney proximal tubule. It belongs to a family of water channels, expressed in all kingdoms of life, which facilitate the flux of water molecules across membranes. Humans express 13 AQP isoforms in tissue-specific manner differentially. Each isoform possesses unique substrate permeability characteristics and being regulated in different ways.

Basic Information of AQP0
Protein Name Aquaporin-0
Gene Name MIP
Aliases Lens fiber major intrinsic protein, MIP26, MP26, Aquaporin-CHIP, Urine water channel
Organism Homo sapiens (Human)
UniProt ID P30301
Transmembrane Times 8
Length (aa) 263

Function of AQP0 Membrane Protein

AQP0 is a water channel that is exclusively expressed in the mammalian eye lens and whose permeability is directly modulated by CaM. AQP0 serves a dual function in the lens by acting as a water channel or as an adhesive protein mediating cell-cell adhesive junctions. The Ca2+-dependent interaction between Ca2+–CaM and the cytoplasmic C-terminal domain of AQP0 regulates the water permeability. The binding of Ca2+/CaM to AQP0 results in the closing of partial pore. The phosphorylation of AQP0 by anchored PKA (AKAP2/PKA complex) can abolish the binding of CaM, which can keep AQP0 in the open conformation and functioning at maximal activity. AQP0 is expressed in the eye lens highly because it serves the critical function of maintaining the transparency of this organ required for our vision. The misregulation of AQP0 leads to a clouding of the eye lens, known as cataracts, which is the leading cause of blindness in the world.

Pseudoatomic model of the AQP0–CaM complex displaying two CaM molecules Fig.1 Pseudoatomic model of the AQP0–CaM complex displaying two CaM molecules (Reichow, 2013).

Application of AQP0 Membrane Protein in Literature

  1. Reichow S.L., et al. Allosteric mechanism of water-channel gating by Ca2+–calmodulin. Nature Structural &Amp; Molecular Biology. 2013, 20:1085. PubMed ID: 23893133

    Authors in this group apply EM to elucidate the pseudoatomic structure of full-length mammalian AQP0 in complex with CaM and how this signaling protein modulates water-channel function.

  2. Gonen T., et al. Aquaporin-0 membrane junctions reveal the structure of a closed water pore. Nature. 2004, 429:193. PubMed ID: 15141214

    This article reports that structure of the AQP0 membrane junction as determined by electron crystallography. The junction is formed by three localized interactions between AQP0 molecules in adjoining membranes, mainly mediated by proline residues conserved in Aquaporin-0 from different species but not present in most other aquaporins.

  3. Reichow S.L., et al. Non-canonical binding of calmodulin to aquaporin-0: implications for channel regulation. Structure. 2008,16(9):1389-1398. PubMed ID: 18786401

    Authors in this group use a combination of biochemical methods and NMR spectroscopy to probe the interaction between AQP0 and CaM in a calcium-dependent manner, which suggests possible structural co-operativity between monomers within the tetramer.

  4. Gold M.G., et al. AKAP2 anchors PKA with aquaporin-0 to support ocular lens transparency. EMBO Molecular Medicine. 2012, 4(1):15-26. PubMed ID: 22095752

    Authors in this group use a variety of cellular and biochemical approaches to discover that products of the A-kinase anchoring protein 2 gene (AKAP2/AKAP-KL) form a stable complex with AQP0 to sequester protein kinase A (PKA) with the channel.

  5. Kumari S.S., et al. Role of Aquaporin 0 in lens biomechanics. Biochem. Biophys. Res. Commun. 2015, 462(4):339-345. PubMed ID: 25960294

    This article shows that AQP0 could be an important component in establishing and/or maintaining the overall lens biomechanics for the first time.

AQP0 Preparation Options

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  1. Reichow S L., et al. (2013). Allosteric mechanism of water-channel gating by Ca2+–calmodulin. Nature Structural &Amp; Molecular Biology. 20:1085.

All listed customized services & products are for research use only, not intended for pharmaceutical, diagnostic, therapeutic or any in vivo human use.

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