Localization of electrogenic Na/bicarbonate cotransporter NBCe1 variants in rat brain

Abstract

The activity of HCO 3 − transporters contributes to the acid-base environment of the nervous system.In the present study, we used in situ hybridization, immunoblotting, immunohistochemistry, and immunogold electron microscopy to localize electrogenic Na/bicarbonate cotransporter NBCe1 splice variants (-A, -B, and -C) in rat brain. The in situ hybridization data are consistent with NBCe1-B and -C, but not -A, being the predominant NBCe1 variants in brain, particularly in the cerebellum, hippocampus, piriform cortex, and olfactory bulb. An antisense probe to the B and C variants strongly labeled granule neurons in the dentate gyrus of the hippocampus, and cells in the granule layer and Purkinje layer (e.g., Bergmann glia) of the cerebellum. Weaker labeling was observed in the pyramidal layer of the hippocampus and in astrocytes throughout the brain. Similar, but weaker labeling was obtained with an antisense probe to the A and B variants. In immunoblot studies, antibodies to the A and B variants (αA/B) and C variant (αC) labeled ~130-kDa proteins in various brain regions. From immunohistochemistry data, both αA/B and αC exhibited diffuse labeling throughout brain, but αA/B labeling was more intracellular and punctate. Based on co-localization Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. studies with antibodies to neuronal or astrocytic markers, αA/B labeled neurons in the pyramidal layer and dentate gyrus of the hippocampus, as well as cortex. αC labeled glia surrounding neurons (and possibly neurons) in the neuropil of the Purkinje cell layer of the cerebellum, the pyramidal cell layer and dentate gyrus of the hippocampus, and the cortex. According to electron microscopy data from the cerebellum, αA/B primarily labeled neurons intracellularly and αC labeled astrocytes at the plasma membrane. In summary, the B and C variants are the predominant NBCe1 variants in rat brain and exhibit different localization profiles. NIH Public Access

Defective membrane expression of the Na + -HCO 3 − cotransporter NBCe1 is associated with familial migraine

“…Thus, enhanced neurotransmitter release by CACNA1A mutations, excessive neuronal firing by SCN1A mutations, or impaired clearance of K + and/or glutamate by ATP1A2 mutations can all induce CSD (6). Neuronal excitation also leads to a transient extracellular alkalosis, possibly mediated by Ca 2+ /H + exchange (7,29). However, glial cell depolarization causes glial cell acid secretion via inward electrogenic Na + -HCO 3 − cotransport, i.e., DIA (7,19), overwhelming the initial extracellular alkalosis.…”

Modular structure of sodium-coupled bicarbonate transporters

“…4). NBCe1-C is predominantly expressed in the brain (Bevensee et al, 2000), particularly in glial cells (Majumdar et al, 2008) where -as proposed for electrogenic NCBT activity in leech glia (Deitmer 1992;Rose and Dietmer, 1994) -NBCe1 activity could help to counter changes in extracellular pH resulting from neuronal firing.…”

Pathophysiological Roles of Mutations in the Electrogenic Na+-HCO - Cotransporter NBCe1

“…NBCe1B is widely expressed in several tissues including pancreatic ducts, intestinal tracts, ocular tissues, and brain [2,12,13,[19][20][21][22]. In the basolateral membranes of pancreatic ducts NBCe1B is thought to mediate bicarbonate uptake into cells, which may be essential for the bicarbonate secretion from pancreas [23][24][25].…”

“…Bevensee et al initially reported that the expression of NBCe1B is more abundant in astrocytes than in neuron, while NBCe1C show the reverse pattern of expression [18]. However, the expression of NBCe1C was also found in rat astrocytes [22]. Despite the intensive expression of NBCe1 in brain and the potential contribution of NBCe1 to the extracellular pH regulation in brain, the physiological significance of NBCe1 in brain had still remained speculative.…”