Functional significance of O‐GlcNAcylation of ICln in the regulation of cellular volume

Abstract

O‐GlcNacylation (O‐GlcNAc) is a post‐translational modification of serine or threonine residues of nuclear and cytoplasmic proteins and occurs via conjugation to a single monosaccharide, the N‐acetylglucosamine. O‐GlcNAc modification intervenes in a wide variety of physiological and pathological processes, and negatively affects the regulation of cellular volume with a molecular mechanism still unknown. Recently, the protein ICln, crucial in the activation of a chloride conductance (IClswell) after anisosmotic cell swelling, has been found to be O‐GlcNacylated. Mass spectrometry and bioinformatics show multiple O‐GlcNAc modification sites, of which the impact on ICln function is unknown. To explore the functional significance of O‐GlcNAc modification of ICln, the wild type and different mutant forms of ICln have been expressed in a heterologous system and characterized by whole‐cell patch‐clamp in the presence of normal or elevated O‐GlcNAc levels. The results show that: I) O‐GlcNAc elevation suppresses the ICln‐induced current; II) IClnT223A is functional and sensitive to O‐GlcNAc elevation; III) IClnS193X loses most of its activity, though the residual current is sensitive to O‐GlcNAc elevation; IV) IClnS67A is functional but insensitive to O‐GlcNAc elevation; V) the IClnS67T‐induced current is lower compared to the wild type, and is no longer responsive to O‐GlcNAc elevation. Overall, the evidence obtained indicates that O‐GlcNAcylation of ICln at the level of Serine 67 leads to suppression of the ICln‐induced current and may disclose the mechanism by which O‐GlcNAc elevation alters the regulation of cellular volume. We suggest that the protein ICln may represent a novel target in the prevention or treatment of pathological states characterized by chronically elevated O‐GlcNAcylation levelsThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.