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Role of the transmembrane and extracytoplasmic domain of beta subunits in subunit assembly, intracellular transport, and functional expression of Na,K-pumps



The ubiquitous Na,K- and the gastric H,K-pumps are heterodimeric plasma membrane proteins composed of an alpha and a beta subunit. The H,K- ATPase beta subunit (beta HK) can partially act as a surrogate for the Na,K-ATPase beta subunit (beta NK) in the formation of functional Na,K- pumps (Horisberger et al., 1991. J. Biol. Chem. 257:10338-10343). We have examined the role of the transmembrane and/or the ectodomain of beta NK in (a) its ER retention in the absence of concomitant synthesis of Na,K-ATPase alpha subunits (alpha NK) and (b) the functional expression of Na,K-pumps at the cell surface and their activation by external K+. We have constructed chimeric proteins between Xenopus beta NK and rabbit beta HK by exchanging their NH2-terminal plus transmembrane domain with their COOH-terminal ectodomain (beta NK/HK, beta HK/NK). We have expressed these constructs with or without coexpression of alpha NK in the Xenopus oocyte. In the absence of alpha NK, Xenopus beta NK and all chimera that contained the ectodomain of beta NK were retained in the ER while beta HK and all chimera with the ectodomain of beta HK could leave the ER suggesting that ER retention of unassembled Xenopus beta NK is mediated by a retention signal in the ectodomain. When coexpressed with alpha NK, only beta NK and beta NK/HK chimera assembled efficiently with alpha NK leading to similar high expression of functional Na,K-pumps at the cell surface that exhibited, however, a different apparent K+ affinity. beta HK or chimera with the transmembrane domain of beta HK assembled less efficiently with alpha NK leading to lower expression of functional Na,K-pumps with a different apparent K+ affinity. The data indicate that the transmembrane domain of beta NK is important for efficient assembly with alpha NK and that both the transmembrane and the ectodomain of beta subunits play a role in modulating the transport activity of Na,K- pumps

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    1. (1989). A general method of site-specific mumgenesis using a modification of the Thermus aquaticus polymerase chain reaction.
    2. (1989). A marker of acid-secreting membrane movement in rat parietal cells.
    3. (1991). A negative slope in the current-voltage relationship of the Na+/K + pump in Xenopus oocytes produced by reduction of external K +.
    4. (1989). A role for the B-subunit in the expression of functional Na+-K+-ATPase in Xenopus oocytes.
    5. (1987). A1-dosterone regulation of Na + transport and Na+-K*-ATPase in A6 cells: Role of growth conditions.
    6. (1992). Assembly of a hybrid from the ct subunit of Na*/K÷-ATPase and the/~ subunit of H+/K +-ATPase.
    7. (1992). B~-subunits and B3-subunits can associate with presynthesized o~-subunits of Xenopus oocyte
    8. (1988). Both VP2 and VP3 are synthesized from each of the alternatively spliced late 19S RNA species of simian virus 40.
    9. (1991). Cell surface transport, oligomerization and endocytosis of chimeric type-II glycoproteins. Role of cytoplasmic and anchor domains.
    10. (1990). Characterization ofa/~-subunit of the gastric H*/K+-transporting ATPase.
    11. (1991). Coexpression of c~ with putative B3 subunits results in functional Na÷/K + pumps in Xenopus oocytes.
    12. (1989). Control of protein exit from the endoplasmic reticulum.
    13. (1991). Cytoplasmic and transmembrane domain deletions of Na,K-ATPase B-subunit. Effects on subunit assembly and intracellular transport.
    14. (1977). DNA sequencing with chainterminating inhibitors.
    15. (1984). Efficient in vitro synthesis of biologically active RNA and RNA hybridization probes from plasmids containing a bacteriophage SP6 promoter. Nucleic Acids Res.
    16. (1992). Evidence of a role for the Na,K-ATPase /3-subanit in active cation transport.
    17. (1987). Expression of hybrid (Na++K+)-ATPase molecules after transfection of mouse Ltk- cells with DNA encoding the ~-subunit of an avian brain sodium pump.
    18. (1992). High-affinity ouabain binding by yeast cells expressing Na+,K+-ATPase a-subanits and the gastric H+,K+-ATPase fl-subunit.
    19. (1982). Hormonal regulation of (Na+,K+)-ATPase biosynthesis in the toad bladder.
    20. (1981). Immunochemical evidence for a transmembrane orientation of both the (Na÷,K+)-ATPase subunits.
    21. (1985). Membrane insertion of ~- and B-subunits of Na+,K÷-ATPase.
    22. (1991). Molecular analysis of Na,KATPase subunit assembly.
    23. (1990). Mutual dependence of Na,K-ATPase ¢x-subunits and B-subunits for correct posttranslational processing and intracellular transport.
    24. (1988). Ouabaln-sensitive (Na++K÷)-ATPase activity expressed in mouse L cells by transfection with DNA encoding the a-subunit of an avian sodium pump.
    25. (1991). Peptide-binding specificity of the molecular chaperone Bip.
    26. (1992). Primary sequence and functional expression of a novel ouabaln-resistant Na,KATPase. The/~-subanit modulates potassium activation of the Na,K-pump.
    27. (1989). Primary sequence of Xenopus laevis Na+,K *-ATPase and its localization in A6 kidney cells.
    28. (1992). Processing, intracellular transport and functional expression of endogenous and exogenous ct-B3 Na,K-ATPase complexes in Xenopus oocytes.
    29. (1989). Protein oligomerization in the endoplasmic reticulum.
    30. (1988). Regulation of protein export from the endoplasmic reticulum.
    31. (1992). Role of transmembrane domain interactions in the assembly of class-II MHC molecules. Science (Wash.
    32. (1988). Structural basis for E~-E2 conformational transition in Na,K-pump and Ca-pump protein.
    33. (1992). The adhesion molecule on glia (AMOG/B2) and ~t~ subunits assemble to functional sodium pumps in Xenopus oocytes.
    34. (1991). The functional role of the B-subunit in the maturation and intracellular transport of Na,K-ATPase.
    35. (1990). The gastric H+,K+-ATPase.
    36. (1991). The H,K-ATPase /3-subanit can act as a surrogate for the B-subunit of Na,K-pumps,
    37. (1992). The N-terminal domains of acetylcholine receptor subunits contain recognition signals for the initial steps of receptor assembly.

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