Phosphohippolin expression in the rat central nervous system

Kadowaki, Kae; Sugimoto, Katsuyoshi; Yamaguchi, Fuminori; Song, Tao; Watanabe, Yasuo; Singh, Kuldeep; Tokuda, Masaaki

doi:10.1016/j.molbrainres.2004.03.021

Cited by 49 publications

(48 citation statements)

References 27 publications

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“…3). FXYD6 shares highest homology with its mammalian counterpart (Table 3), which is highly expressed in the brain (36), but also in epithelial cells of the inner ear (21). It is possible that a difference in basal expression in other tissues than brain may result from different degrees of innervation.…”

Section: Discussionmentioning

confidence: 99%

Identification of FXYD protein genes in a teleost: tissue-specific expression and response to salinity change

Tipsmark¹

2008

American Journal of Physiology-Regulatory, Integrative and Comp

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It is increasingly clear that alterations in Na+-K+-ATPase kinetics to fit the demands in specialized cell types is vital for the enzyme to execute its different physiological roles in diverse tissues. In addition to tissue-dependent expression of isoforms of the conventional subunits, alpha and beta, auxiliary FXYD proteins appear to be essential regulatory components. The present study identified genes belonging to this family in Atlantic salmon by analysis of expressed sequence tags. Based on the conserved domain of these small membrane proteins, eight expressed FXYD isoforms were identified. Phylogenetic analysis suggests that six isoforms are homologues to the previously identified FXYD2, FXYD5, FXYD6, FXYD7, FXYD8, and FXYD9, while two additional isoforms were found (FXYD11 and FXYD12). Using quantitative PCR, tissue-dependent expression of the different isoforms was analyzed in gill, kidney, intestine, heart, muscle, brain, and liver. Two isoforms were expressed in several tissues (FXYD5 and FXYD9), while six isoforms were distributed in a discrete manner. In excitable tissues, two isoforms were highly expressed in brain (FXYD6 and FXYD7) and one in skeletal muscle (FXYD8). In osmoregulatory tissues, one isoform was expressed predominantly in gill (FXYD11), one in kidney (FXYD2), and one equally in kidney and intestine (FXYD12). Expression of several FXYD genes in kidney and gill differed between fresh water and seawater salmon, suggesting significance during osmoregulatory adaptations. In addition to identifying novel FXYD isoforms, these studies are the first to show the tissue dependence in their expression and modulation by salinity in any teleosts.

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Section: Discussionmentioning

confidence: 99%

Identification of FXYD protein genes in a teleost: tissue-specific expression and response to salinity change

Tipsmark¹

2008

American Journal of Physiology-Regulatory, Integrative and Comp

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“…In the brain, expression studies during development suggest a role in neuronal excitability during postnatal development and in the adult brain (47,78).…”

Section: Fxyd4 (Chif)mentioning

confidence: 99%

FXYD proteins: new regulators of Na-K-ATPase

Geering¹

2006

American Journal of Physiology-Renal Physiology

327

308

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FXYD proteins belong to a family of small-membrane proteins. Recent experimental evidence suggests that at least five of the seven members of this family, FXYD1 (phospholemman), FXYD2 (gamma-subunit of Na-K-ATPase), FXYD3 (Mat-8), FXYD4 (CHIF), and FXYD7, are auxiliary subunits of Na-K-ATPase and regulate Na-K-ATPase activity in a tissue- and isoform-specific way. These results highlight the complexity of the regulation of Na+ and K+ handling by Na-K-ATPase, which is necessary to ensure appropriate tissue functions such as renal Na+ reabsorption, muscle contractility, and neuronal excitability. Moreover, a mutation in FXYD2 has been linked to cases of human hypomagnesemia, indicating that perturbations in the regulation of Na-K-ATPase by FXYD proteins may be critically involved in pathophysiological states. A better understanding of this novel regulatory mechanism of Na-K-ATPase should help in learning more about its role in pathophysiological states. This review summarizes the present knowledge of the role of FXYD proteins in the modulation of Na-K-ATPase as well as of other proteins, their regulation, and their structure-function relationship.

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“…[20][21][22][23] and are believed to play a role in neuron excitability during postnatal development and in the adult brain. 8,24 Membrane proteins belonging to what is now recognized as the FXYD family were first discovered, in association with the Na,K-ATPase, 4 or as a major substrate of hormonestimulated phosphorylation in sarcolemma. 25 The subsequent sequencing and identification of additional proteins, with similar structural and functional features, pointed to the existence of a family of homologous membrane proteins involved in ion transport regulation.…”

Section: Introductionmentioning

confidence: 99%

Correlation of Gene and Protein Structures in the FXYD Family Proteins

Franzin

Thai

et al. 2005

Journal of Molecular Biology

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The FXYD family proteins are auxiliary subunits of the Na,K-ATPase, expressed primarily in tissues that specialize in fluid or solute transport, or that are electrically excitable. These proteins range in size from about 60 to 160 amino acid residues, and share a core homology of 35 amino acid residues in and around a single transmembrane segment. Despite their relatively small sizes, they are all encoded by genes with six to nine small exons. We show that the helical secondary structures of three FXYD family members, FXYD1, FXYD3, and FXYD4, determined in micelles by NMR spectroscopy, reflect the structures of their corresponding genes. The coincidence of helical regions, and connecting segments, with the positions of intron-exon junctions in the genes, support the hypothesis that the FXYD proteins may have been assembled from discrete structural modules through exon shuffling. KeywordsFXYD; Na,K-ATPase; NMR structure; membrane protein; gene The FXYD family proteins are tissue-specific and physiological-state-specific auxiliary subunits of the Na, K-ATPase, the primary enzyme responsible for maintaining the equilibrium of Na and K ion concentrations across animal cell membranes. [1][2][3] All of the FXYD genes are expressed in the early stages of fetal life, with prevalence in tissues that specialize in fluid or solute transport, or that are electrically excitable. In keeping with their distribution in tissues, several FXYD family members have been shown to regulate ion transport by binding and modulating the activity of Na, K-ATPase molecules. [2][3][4][5][6][7][8][9][10][11] In addition, certain FXYD family members can induce ionic currents in Xenopus oocytes, or in phospholipid bilayers, although the direct formation of ion channels has not been demonstrated in vivo. [12][13][14][15][16] Seven FXYD family members have been identified in mammals. FXYD1 (PLM; phospholemman) is the principal substrate of hormone-stimulated phosphorylation by cAMP-dependent protein kinase A and C in sarcolemma heart. 17 FXYD2 (gamma), unique in the family for having two alternative splice variants (FXYD2a and FXYD2b), and FXYD4 (CHIF; channel-inducing factor; corticosteroid hormone induced factor), are each expressed in distinct, specialized segments of the kidney, with unique expression patterns that help explain the physiological differences in Na,K-ATPase activity among the nephron segments. 5,6,13,18,19 Two family members, FXYD3 (Mat8; mammary tumor protein 8 kDa) and FXYD5 (RIC; resembles ion channel; dyshaderin), are expressed in cancers and play a role in tumor progression. [20][21][22][23] and are believed to play a role in neuron excitability during postnatal development and in the adult brain. 8,24 Membrane proteins belonging to what is now recognized as the FXYD family were first discovered, in association with the Na,K-ATPase, 4 or as a major substrate of hormonestimulated phosphorylation in sarcolemma. 25 The subsequent sequencing and identification of additional proteins, with similar structural and functi...

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Phosphohippolin expression in the rat central nervous system

Cited by 49 publications

References 27 publications

Identification of FXYD protein genes in a teleost: tissue-specific expression and response to salinity change

Identification of FXYD protein genes in a teleost: tissue-specific expression and response to salinity change

FXYD proteins: new regulators of Na-K-ATPase

Correlation of Gene and Protein Structures in the FXYD Family Proteins

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