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The oculocerebrorenal syndrome of Lowe protein (OCRL) inhibits the Na/bicarbonate cotransporter NBCe1 expressed in Xenopus laevis oocytes.
Author(s) -
Michenkova Marie,
Thornell Ian M.,
Peng JiBen,
Bevensee Mark O.
Publication year - 2018
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.2018.32.1_supplement.lb443
Subject(s) - medicine , endocrinology , chemistry , xenopus , reabsorption , cotransporter , phosphatase , microbiology and biotechnology , biology , gene , biochemistry , phosphorylation , sodium , kidney , organic chemistry
The electrogenic Na/HCO 3 cotransporter NBCe1 regulates intracellular pH in many tissues and contributes to solute reabsorption/secretion in epithelia. NBCe1 is modulated by hormones, classic second messengers, and other signaling molecules/ions. We previously reported that both the phospholipid PIP 2 itself and its hydrolysis to IP 3 (Ca 2+ ) stimulates the activity of NBCe1 expressed in oocytes. In this preparation, activating a co‐expressed voltage‐sensitive phosphatase (VSP) that dephosphorylates PIP 2 to PIP without stimulating IP 3 /Ca 2+ signaling decreases NBCe1 activity. In the current study, we examined the effect of the PIP 2 ‐lowering phosphatase, inositol polyphosphate 5‐phosphatase encoded by the oculocerebrorenal syndrome of Lowe gene ( OCRL ) on the activity of NBCe1 variants expressed in oocytes. Mutations and variants of OCRL lead to Dent disease type 2, as well as Lowe Syndrome, which is characterized by cataracts, intellectual disability, basal ganglia calcification, and proximal renal tubular acidosis (pRTA). Using the 2‐electrode voltage‐clamp technique, we found that oocytes co‐expressing human OCRL with NBCe1‐A (both HA tagged) displayed a characteristic NBC‐mediated, HCO 3 – ‐induced outward current (I NBC ) that was 59% smaller than oocytes expressing NBCe1‐A. We also observed OCRL inhibition of HA‐tagged NBCe1‐B and ‐C. We obtained similar results after replacing the HA tag on NBCe1‐A with a FLAG tag. The OCRL‐induced decrease in I NBC could be explained by a decrease in NBCe1 expression at the plasma membrane. Co‐expressing OCRL caused a 44% decrease in I NBC and a parallel 33% decrease in FLAG‐tagged NBCe1‐A oocyte surface expression as determined by single‐oocyte chemiluminescence. Thus, a physiological phosphatase that lowers PIP 2 can regulate the activity and/or expression of NBCe1. Altered activity/expression of NBCe1 caused by mutant OCRL variants seen in Dent disease and Lowe Syndrome may contribute to observed patient symptoms, especially pRTA. This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .