Regulation of electrogenic Na+/HCO3- cotransporter 1 (NBCe1) in mouse cortical astrocytes and its dependence on m-TOR mediated phosphorylation of Ser245.

ABSTRACT: Astrocytes are pivotal responders to alterations of extracellular pH, primarily by regulation of their “master” acid-base transporter, the membrane-bound electrogenic Na+/bicarbonate cotransporter 1 (NBCe1). Here, we describe an mTOR-dependent and NBCe1-mediated astroglial response to extracellular acidosis. Using primary mouse cortical astrocytes we investigated the effect of long-term extracellular metabolic acidosis on regulation of NBCe1 and elucidated the underlying molecular mechanisms by immunoblotting, biotinylation of surface proteins, intracellular H+ recording using the H+ -sensitive dye 2′,7′-bis-(carboxyethyl)-5-(and-6)-carboxyfluorescein (BCECF), and phosphoproteomic analysis. The results showed significant increase of NBCe-1-mediated recovery of intracellular pH from acidification in wild-type astrocytes, but not in cortical astrocytes from NBCe1-deficient mice. Acidosis-induced upregulated NBCe1 activity was prevented following inhibition of mTOR signaling by rapamycin. In contrast, during acidosis or following exposure of astrocytes to rapamycin, surface protein abundance of NBCe1 remained comparable. Furthermore, NBCe1 activity was dependent on phosphorylation state of Ser245, a residue conserved in all NBCe1 variants. Mutational analysis suggested that phosphorylation state of Ser245 is regulated by mTOR and is inversely correlated with NBCe1 transport activity. Our results identify pSer245 as a novel regulator of NBCe1 functional expression. We propose that context-dependent and mTOR-mediated multisite phosphorylation of serine residues of NBCe1 is likely to be a potent mechanism contributing to the response of astrocytes to acid/base challenges during pathophysiological conditions.

ORGANISM(S): Mus Musculus

SUBMITTER: Christina Ludwig  

PROVIDER: PXD024529 | panorama | Wed Jan 12 00:00:00 GMT 2022

REPOSITORIES: PanoramaPublic