The lipidation profile of aquaporin-0 correlates with the acyl composition of phosphoethanolamine lipids in lens membranes

Abstract

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The Role of Aquaporins in Ocular Lens Homeostasis

“…AQP0 is modified by palmitoylation (C16:0, +238 Da) and oleic acid (C18:1, +264 Da) at N-terminal M1 and C-terminal K238 in bovine and human lenses [ 95 ]. Other fatty acid modifications to AQP0 have also been reported [ 96 ]. Non-lipidated AQP0 was detected in detergent-soluble membrane fractions (DSM), whereas lipidated AQP0 was detected exclusively in detergent-resistant membrane (lipid raft) fractions.…”

Lysine Fatty Acylation: Regulatory Enzymes, Research Tools, and Biological Function

“…They identified AQP0 as containing two fatty acylations: one on the N-terminal methionine and one on a highly conserved lysine. The identity of AQP0 KFA modification varies from C16 to C20 with up to 4 desaturations at ratios closely resembling the abundance of phosphoethanolamine lipids in lens membranes (Ismail et al, 2016). This suggests that either the modification is accumulating non-enzymatically or that a potential KFA transferase has limited preference in acyl group.…”

Far from Inert: Membrane Lipids Possess Intrinsic Reactivity That Has Consequences for Cell Biology

“…Neither site is completely lipidated. This combination of features bears all the hallmarks of an intrinsic lipidation process …”

“…In many cases, lipidated products evade detection because they are insoluble or elute in the wash phase at the end of a proteomics run. For example, N‐terminal lipidated fragments of aquaporin‐0 (AQP0) were found in mobile phases with >95% acetonitrile during LC‐MS analyses of tryptic digests of the protein It is difficult to predict the likely sites of lipidation on any molecule because the reactivity is structure‐based, depending, to a significant degree, on the relative positioning of the molecule with respect to the membrane.…”