Human ATP1AL1 and corresponding genes of other mammals encode the catalytic K

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The molecular basis of active ion transport in secretory glands such as the prostate is not well characterized. Rat nongastric H-K-ATPase is expressed at high levels in distal colon surface cell apical membranes and thus is referred to as “colonic.” Here we show that the ATPase is expressed in rodent prostate complex in a lobe-specific manner. RT-PCR and Western blot analyses indicate that rat nongastric H-K-ATPase α-subunit (αng) mRNA and protein are present in coagulating gland (anterior prostate) and lateral and dorsal prostate and absent from ventral lobe, whereas Na-K-ATPase α-subunit is present in all lobes. RT-PCR analysis shows that Na-K-ATPase α4 and α3 and gastric H-K-ATPase α-subunit are not present in significant amounts in all prostate lobes. Relatively low levels of Na-K-ATPase α2were found in lateral, dorsal, and anterior lobes. αngprotein expression is anteriodorsolateral: highest in coagulating gland, somewhat lower in dorsal lobe, and even lower in lateral lobe. Na-K-ATPase protein abundance has the reverse order: expression in ventral lobe is higher than in coagulating gland. αngprotein abundance is higher in coagulating gland than distal colon membranes. Immunohistochemistry shows that in rat and mouse coagulating gland epithelium αng protein has an apical polarization and Na-K-ATPase α1 is localized in basolateral membranes. The presence of nongastric H-K-ATPase in rodent prostate apical membranes may indicate its involvement in potassium concentration regulation in secretions of these glands.

Change in gene functions (gene cooption) is one of the key mechanisms of molecular evolution. Genes can acquire new functions via alteration in properties of encoded proteins and/or via changes in temporal or spatial regulation of expression. Here we demonstrate radical changes in the functions of orthologous ATP1B4 genes during evolution of vertebrates. Expression of ATP1B4 genes is brain-specific in teleost fishes, whereas it is predominantly muscle-specific in tetrapods. The encoded ␤m-proteins in fish, amphibian, and avian species are ␤-subunits of Na,K-ATPase located in the plasma membrane. In placental mammals ␤m-proteins lost their ancestral functions, accumulate in nuclear membrane of perinatal myocytes, and associate with transcriptional coregulator Ski-interacting protein (SKIP). Through interaction with SKIP, eutherian ␤m acquired new functions as exemplified by regulation of TGF-␤-responsive reporters and by augmentation of mRNA levels of Smad7, an inhibitor of TGF-␤ signaling. Thus, orthologous vertebrate ATP1B4 genes represent an instance of gene cooption that created fundamental changes in the functional properties of the encoded proteins.ATP1B4 ͉ gene cooption ͉ skeletal muscle development ͉ TGF-␤ ͉ Smad7

The physiological functions of nongastric (colonic) H-K-ATPase (gene symbol Atp12a), unlike those of Na-K-ATPase and gastric H-K-ATPase, are poorly understood. It has been suggested that it pumps Na+ more efficiently than H+; however, so far, there is no direct evidence that it pumps H+ in vivo. Previously, we found that the nongastric H-K-ATPase alpha-subunit is expressed in apical membranes of rodent anterior prostate epithelium, in a complex with the Na-K-ATPase beta1-subunit. Here we report the effects of Atp12a gene ablation on polarization of the beta1-subunit and secretory function of the anterior prostate. In nongastric H-K-ATPase-deficient prostate, the Na-K-ATPase alpha-subunit resided exclusively in basolateral membranes; however, the beta1-subunit disappeared from apical membranes, demonstrating that beta1 is an authentic subunit of nongastric H-K-ATPase in vivo and that apical localization of beta1 in the prostate is completely dependent on its association with the nongastric H-K-ATPase alpha-subunit. A remarkable reduction in acidification of anterior prostate fluids was observed: pH 6.38 +/- 0.14 for wild-type mice and 6.96 +/- 0.10 for homozygous mutants. These results show that nongastric H-K-ATPase is required for acidification of luminal prostate fluids, thereby providing a strong in vivo correlate of previous functional expression studies demonstrating that it operates as a proton pump.

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Zhao, Hao, Nikolay B. Pestov, Tatyana V. Korneenko, Mikhail I. Shakhparonov, and Nikolai N. Modyanov. Accumulation of ␤ m, a structural member of X,K-ATPase ␤-subunit family, in nuclear envelopes of perinatal myocytes. Am J Physiol Cell Physiol 286: C757-C767, 2004. First published December 3, 2003 10.1152/ ajpcell.00358.2003.-Recently discovered muscle-specific ␤ m protein is structurally closely related to the X,K-ATPase ␤-subunits. However, it has a number of unique properties such as predominant localization in intracellular stores and lack of association with known X,K-ATPase ␣-subunits on heterologous coexpression. In this study, the primary structure of mouse ␤ m was determined and developmental regulation of the gene (ATP1B4) was analyzed. The expression is first detected at day 14 of gestation, is sharply increased at day 16, and reaches its maximum at day 18. After birth, the expression quickly decreases and is hardly detectable in adult mice. A more detailed subcellular localization study was undertaken, and its results indicate that ␤ m not only is located in sarcoplasmic reticulum but is concentrated in nuclear envelopes of both prenatal and postnatal skeletal muscles. Immunohistochemical studies show that ␤ m is specific to myocytes and, at the subcellular level, many nuclear envelopes are intensively labeled in both fetal and newborn skeletal muscles. Accordingly, ␤ m is detected by immunoblotting in purified nuclei and nuclear membranes from neonatal skeletal muscles. On transfection of human rhabdomyosarcoma cell line RD, green fluorescent proteintagged ␤ m resides intracellularly with significant enrichment in nuclear envelopes, whereas ␤ m with transmembrane domain deleted localizes in both cytoplasm and nucleoplasm. Nuclear ␤ m apparently is not in association with Na,K-ATPase because we never detected its ␣-subunit in myonuclear membranes. These results indicate that ␤ m has a specialized function in mammalian perinatal myocytes, different from functions of other X,K-ATPase ␤-subunits. The unique temporospatial distribution of ␤ m protein expression suggests its important role in development of growing skeletal muscle.ATP1B4; sodium, potassium-adenosine 5Ј-triphosphatase; nuclear membrane; skeletal muscle development AMONG MORE THAN 200 P-ATPases identified in prokaryotes and eukaryotes (1), most enzymes have just a single catalytic subunit. However, the animal X,K-ATPases (Na,K-ATPase, gastric H,K-ATPase, and nongastric H,K-ATPase) contain, in addition to the catalytic ␣-subunit, an accessory ␤-subunit. Although major functions such as ATP binding, phosphorylation, and ion transport are performed by the ␣-subunit, the ␣-␤ interaction is required for maturation, stability, and translocation of the ATPases to plasma membrane (4, 44). Moreover, the ␤-subunit seems to be related to K transport, the unique feature of the X,K-ATPase family members (16, 45). The ␤-subunit is involved in K affinity and cardiac glycoside sensitivity (25, 45). Different ␣-and ␤-isoform combinations exhibit functiona...

Hampin, homolog of drosophila MSL1, is a partner of histone acetyltransferase MYST1/MOF. Functions of these proteins remain poorly understood beyond their participation in chromatin remodeling complex MSL. In order to identify new proteins interacting with hampin, we screened a mouse cDNA library in yeast two-hybrid system with mouse hampin as bait and found five highconfidence interactors: MYST1, TPR proteins TTC4 and KIAA0103, NOP17 (homolog of a yeast nucleolar protein) and transcription factor GC BP. Subsequently, all these proteins were used as baits in library screenings and more new interactions were found: tumor suppressor RASSF1C and spliceosome component PRP3 for KIAA0103, ring finger RNF10 for RASSF1C, and RNA polymerase II regulator NELF-C for MYST1. The majority of the observed interactions was confirmed in vitro by pull-down of bacterially expressed proteins. Reconstruction of a fragment of mammalian interactome suggests that hampin may be linked to diverse regulatory processes in the nucleus.