An emerging consensus on aquaporin translocation as a regulatory mechanism

Abstract

Water can pass through the cell membrane relatively slowly by diffusion. However, in order to maintain water homeostasis, the rapid and specific regulation of cellular water flow is mediated by the aquaporin (AQP) family of membrane protein water channels. Thirteen human AQPs have been identified to date and the majority are highly specific for water while others show selectivity for water, glycerol and other small solutes. The wide range of tissues that are known to express AQPs is reflected by their involvement in many physiological processes and diseases. Receptor mediated translocation, via hormone activation, is an established method of AQP regulation, especially for AQP2. There is now an emerging consensus that the rapid and reversible translocation of other AQPs from intracellular vesicles to the plasma membrane, triggered by a range of stimuli, can confer increased membrane permeability. This review examines new advances that have identified molecular mechanisms of AQP regulation; these include the role of cytoskeletal proteins, kinases, calcium and retention or localisation signals as well as specific triggers of AQP translocation. This article reviews current knowledge of AQP regulation with a focus on rapid and dynamic regulation of sub-cellular AQP translocation in response to a specific trigger.3

Aquaporins in Infection and Inflammation

“…We hypothesise that an unresolved dysregulation of AQPs lays the foundation for the development of chronic diarrhoeal inflammatory diseases. Both hypotonicity and hypertonicity have been shown to influence the translocation of AQPs [43]. It is likely that in MC the diarrhoea creates an extreme dysregulation in the tonicity leading to a translocation of AQPs which together with an altered expression rate leads to a vicious circle of more watery diarrhoea.…”

“…The function of AQPs is controlled by expression and perhaps foremost by translocation to the cell membranes [43]. The AQPs can rapidly and reversibly translocate to the plasma membrane from intracellular vesicles.…”

“…We are focusing primarily on the AQPs showing larger variations on transcriptional level (AQP1, 8 and 11) but since translocation of AQPs is an important part of normal functioning of water homeostasis [43,253], we will also assess the moderate or unaffected AQPs.…”

Mycorrhizal Fungi to Alleviate Drought Stress on Plant Growth

“…Emerging insights are provided by studies on the regulation of important genes that encode significant components of the cellular water transport system, such as the aquaporins. These components are membrane proteins that channel water, uncharged molecules, across cell membranes in both roots and leaves (Conner et al 2013;Maurel et al 2008). These proteins may even increase root hydraulic conductivity and leaf water potential and decrease the transpiration rate in the leaves of mycorrhizal plants (RuizLozano et al 2006(RuizLozano et al , 2009Aroca et al 2008).…”

“…AM symbiosis improves the plant water content by regulating the properties of plant hydraulics, including root hydraulic conductivity, although some authors have reported an enhanced (Sanchez-Blanco et al 2004;Aroca et al 2008) or reduced (Aroca et al 2007;Ruiz-Lozano et al 2009) effect of AM fungi on this trait. The role of the membrane transporter aquaporins in root hydraulic conductivity at the cellular level and their contributions to the transpiration stream have been investigated (Conner et al 2013;Maurel et al 2008) and will be discussed in the next section.…”