Cell-specific expression of mRNAs encoding Na+,K(+)-ATPase alpha- and beta-subunit isoforms within the rat central nervous system.

Abstract

We have used in situ hybridization histochemistry to analyze the subceilular distribution of mRNAs encoding Na,K-ATPase a-and /3-subunit isoforms in the rat central nervous system. Substantial differences in the cellspecific pattern ofexpression were found for the genes encoding three isoforms of the a subunit. Transcripts of al-subunit genewere detected in virtually all cell types and structures examined. Expression of a2-subunit mRNA was characteristic of glia, whereas a3-subunit transcripts were predominant in neurons. Transcripts encoding the /31 subunit were detected in neurons, whereas /32-subunit mRNA expression was characteristic of glia. mRNA encoding both /3-subunit isoforms was present in choroidal epithelial cells. The distribution pattern of a-and /8-subunit mRNAs in structures throughout the central nervous system is consistent with the possibility of six structurally distinct Na',K+-ATPase isoenzymes.Na',K+-ATPase is the enzymatic activity responsible for active transport of Na' and K+ in most animal cells (1). The enzyme plays a central role in mediating electrical activity of the brain. In neurons, Na',K+-ATPase maintains the Na'and K+ gradients essential for nerve-impulse generation (2). Uptake of neurotransmitters and efflux of calcium from neurons are also coupled to activity ofthe enzyme (3). In glia, Na',K+-ATPase plays a critical role in potassium uptake during periods of neuronal activity (4-6).Na',K+-ATPase has been shown to consist of two subunits. The a subunit is a polypeptide of Mr -100,000 that contains the catalytic site for ATP hydrolysis and serves as the receptor for cardiac glycosides, such as ouabain and digitalis (1). The /3 subunit is a polypeptide ofMr =55,000 the function of which has yet to be established. Molecular cloning has revealed that Na',K+-ATPase a and / subunits are encoded by multigene families. Three a-and two /-subunit genes have been localized to different chromosomes in the mouse (7,8), and cDNA clones encoding three rat a-(al, a2, a3) and two /8-(J1, /32) subunit isoforms have been characterized (9-12). Substantial differences in the tissue and developmental specificity of expression have been found for each a and /3 subunit. al subunits have been detected in virtually all rat tissues (13). In contrast, a2 subunits are expressed predominantly in brain, heart, and lung (13), whereas a3 subunits are expressed in brain (13), pineal gland (14), and retinal photoreceptors (15). Expression of 81 subunits has been detected in brain, heart, and kidney (13), whereas /2 subunits are expressed primarily in brain (16), pineal gland (14), and photoreceptor cells (15). However, the physiological significance for a-and /-subunit isoform diversity has not been clearly explained.Analysis of the cellular distribution of Na',K+-ATPase expression should provide important clues to the normal physiological function of distinct Na',K+-ATPase isoenzymes. Recent studies have described the anatomical distribution of Na',K+-ATPase mRNAs (17-19) and polypeptides (20) within s...

A cluster of differentially expressed signal transduction genes identified by microarray analysis in a rat genetic model of alcoholism

“…30 We found a decrease in mRNA levels for two subunits of the sodium/potassium-specific ATPase, Atp1a2 and Atp1b2, a combination predominantly found in glia. 31 Together with a concomitant downregulation of glial fibrillary acidic protein (Gfap), these genes may reflect gliaspecific alterations in the amygdala. Studies of cerebellar tissue from AA rats have demonstrated downregulated Gfap expression after long-term ethanol consumption, 32 while a cDNA array study of cortical tissue from human alcoholics identified cytoskeleton-related genes, in particular myelin-associated genes and Gfap, as the most prominent dysregulations.…”

The formation of cerebrospinal fluid: Nearly a hundred years of interpretations and misinterpretations

“…The third reason why the choroid plexuses are considered to the main site of formation should be the fact that the observations mentioned so far were accompanied by a significant number of concurrent studies that pointed to CSF formation by the choroid plexuses (Dandy, 1919;de Rougemont et al, 1960;Pollay et al, 1972;Weed, 1914;Welch, 1963) , and the secretory character of the choroid plexuses was confirmed by the application of the molecular biological methods during the past two decades (Brown et al, 2004;Johanson, 2008;Kanaka et al, 2001;Li et al, 2002;Oshio et al, 2005;Praetorius et al, 2004;Speake et al, 2003;Watts et al, 1991;Zlokovic et al, 1993).…”

“…The secretory character of choroid plexuses that involves pumps, cotransporters and antiporters, ion channels and aquaporins has been confirmed during the past 15 years by the application of molecular biological methods (Brown et al, 2004;Johanson, 2008;Kanaka et al, 2001;Li et al, 2002;Oshio et al, 2005;Praetorius et al, 2004;Speake et al, 2003;Watts et al, 1991;Zlokovic et al, 1993).…”

Distribution of immunoreactive alpha- and beta-subunit isoforms of Na,K-ATPase in the gerbil inner ear.

“…Localization of the a3/pl complex in neurons and nerve endings of the cochlea and vestibular system was not unexpected, as this subunit combination predominates in neurons (Hieber et al, 1991;Watts et al, 1991;Hsu and Guidotti, 1989;Urayama et al, 1989). Abundant Na,K-AlTase in neurons functions to reestablish the resting membrane potential after the generation of action potentials.…”

“…These isoforms occur in an organand cell type-specific distribution in many tissues including kid-843 ney, brain, pineal gland, eye, liver, heart, and inner ear (Ryan and Watts, 1991;Watts et al, 1991;Sweadner, 1989). The physiological significance of the P-subunit remains obscure, but the a-subunit is thought to mediate catalytic activity.…”