Adaptable and Multifunctional Ion-Conducting Aquaporins

Abstract

Aquaporins function as water and neutral solute channels, signaling hubs, disease virulence factors, and metabolon components. We consider plant aquaporins that transport ions compared to some animal counterparts. These are candidates for important, as yet unidentified, cation and anion channels in plasma, tonoplast, and symbiotic membranes. For those individual isoforms that transport ions, water, and gases, the permeability spans 12 orders of magnitude. This requires tight regulation of selectivity via protein interactions and posttranslational modifications. A phosphorylation-dependent switch between ion and water permeation in AtPIP2;1 might be explained by coupling between the gates of the four monomer water channels and the central pore of the tetramer. We consider the potential for coupling between ion and water fluxes that could form the basis of an electroosmotic transducer. A grand challenge in understanding the roles of ion transporting aquaporins is their multifunctional modes that are dependent on location, stress, time, and development. Expected final online publication date for the Annual Review of Plant Biology, Volume 72 is May 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Dehydrin MsDHN1 improves aluminum tolerance of alfalfa (Medicago sativaL.) by affecting oxalate exudation from root tips

“…Aquaporins are integral membrane proteins and belong to the MIP (major intrinsic protein) superfamily (Maurel et al., 2008). They are mainly divided into five groups: PIPs (PM intrinsic proteins); TIPs (tonoplast intrinsic proteins); NIPs (nodulin‐like intrinsic proteins); SIPs (small basic intrinsic proteins); and XIPs (X intrinsic proteins; Tyerman et al., 2021). AQPs facilitate water and neutral solute to transport across cellular membranes, and play important roles in abiotic stress.…”

“…The lactate in aqueous solution undergoes an pH‐dependent protonation equilibrium with neutral lactic acid, which likely represents the actual substrate form passing the AQP channel (Schmidt et al., 2021). AtPIP2;1/2;2 have a wide range of solute permeability, and are considered as multifunctional conditional transport systems involving abiotic stress (Tyerman et al., 2021). Overexpression of AtPIP2;2 promotes As (III) tolerance by decreasing As accumulation in Arabidopsis (Modareszadeh et al., 2021).…”

Targeting Aquaporins in Novel Therapies for Male and Female Breast and Reproductive Cancers

“…Changes in aquaporin gene expression have been linked to human diseases such as congenital bilateral cataracts [41], obesity [31], nephrogenic diabetes insipidus [42,43], Sjögren's syndrome [44,45], cerebral edema [46,47], pulmonary edema [48], and cancer [9,49,50], to mention a few. Traditional distinctions based on solute selectivity are becoming blurred as more substrates are being added steadily to the growing repertoires of AQP classes [51]. The full spectra of solutes permeable through AQP channels remain to be defined.…”

Expression of a CO2-permeable aquaporin enhances mesophyll conductance in the C4 species Setaria viridis

“…The significant contribution of aquaporins to increased CO 2 diffusion has been demonstrated in C 3 plants (Flexas et al, 2006;Hanba et al, 2004;Sade et al, 2010). Aquaporins have key roles in regulating the movement of water and solutes into roots and between tissues, cells and organelles (Tyerman, McGaughey, Qiu, Yool, & Byrt, 2021). These pore-forming integral membrane proteins can be divided into multiple sub-families depending on their amino acid sequence and sub-cellular localization.…”