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PMID:14625281

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Citation

Cai, X and Lytton, J (2004) Molecular cloning of a sixth member of the K+-dependent Na+/Ca2+ exchanger gene family, NCKX6. J. Biol. Chem. 279:5867-76

Abstract

Bioinformatic and molecular cloning tools were used to identify and isolate cDNA clones from mouse and human tissues that encode the sixth member of the K(+)-dependent Na+/Ca2+ exchanger family, NCKX6. The mouse NCKX6 protein is 585 amino acids long and shares about 62% sequence similarity with previously identified exchangers in the alpha-repeat regions but has little primary sequence similarity outside these regions. NCKX6 transcripts of 4 kb are abundantly expressed in all tissues examined and are thus more broadly distributed than previously described NC(K)X family members. Two alternatively spliced products of this novel gene were identified that encode proteins of different length. The short isoform differs from the full-length isoform at the C-terminal hydrophobic domain as a result of a shift in the reading frame caused by the deletion of two exons. Both NCKX6 isoforms were expressed in HEK-293 cells. Functional analysis by digital imaging of fura-2 loaded transfected HEK-293 cells demonstrated that the short isoform exhibited K(+)-dependent Na+/Ca2+ exchange activity whereas the full-length isoform did not. The latter was retained within the endoplasmic reticulum, whereas the short isoform was present at the plasma membrane in transfected cells. Immunofluorescence studies examining NCKX6 expression in native tissue using an NCKX6-specific antibody showed intense labeling of the cardiac sarcolemmal membrane. The discovery of NCKX6 therefore reveals a novel member of the Na+/Ca2+ exchanger superfamily whose ubiquitous expression in all tissues suggests an important role for K(+)-dependent Na+/Ca2+ exchange in maintaining cellular Ca2+ homeostasis in diverse tissues and cell types.

Links

PubMed Online version:10.1074/jbc.M310908200

Keywords

Alternative Splicing; Amino Acid Sequence; Animals; Blotting, Northern; Calcium/metabolism; Cell Line; Cell Membrane/metabolism; Cloning, Molecular; Computational Biology; DNA, Complementary/metabolism; Fluorescent Antibody Technique, Indirect; Humans; Mice; Microscopy, Fluorescence; Models, Biological; Molecular Sequence Data; Myocardium/metabolism; Potassium/chemistry; Protein Isoforms; Protein Structure, Tertiary; RNA, Messenger/metabolism; Rats; Sarcolemma/metabolism; Sequence Homology, Amino Acid; Sodium-Calcium Exchanger/chemistry; Sodium-Calcium Exchanger/genetics; Sodium-Calcium Exchanger/metabolism; Time Factors; Tissue Distribution; Transfection

Significance

Annotations

Gene product Qualifier GO Term Evidence Code with/from Aspect Extension Notes Status

RAT:NCLX

located_in

GO:0042383: sarcolemma

ECO:0000314: direct assay evidence used in manual assertion

C

Seeded From UniProt

complete

RAT:NCLX

located_in

GO:0005743: mitochondrial inner membrane

ECO:0000314: direct assay evidence used in manual assertion

C

Seeded From UniProt

complete

MOUSE:NCLX

enables

GO:0005432: calcium:sodium antiporter activity

ECO:0000314: direct assay evidence used in manual assertion

F

Seeded From UniProt

complete

MOUSE:NCLX

located_in

GO:0005886: plasma membrane

ECO:0000314: direct assay evidence used in manual assertion

C

Seeded From UniProt

complete

MOUSE:NCLX

acts_upstream_of_or_within

GO:0035725: sodium ion transmembrane transport

ECO:0000314: direct assay evidence used in manual assertion

P

Seeded From UniProt

complete

MOUSE:NCLX

acts_upstream_of_or_within

GO:0070588: calcium ion transmembrane transport

ECO:0000314: direct assay evidence used in manual assertion

P

Seeded From UniProt

complete


See also

References

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