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A novel physiological role for Na, K‐ATPase: Maintenance of nucleoplasmic calcium
Author(s) -
Galva Charitha,
Artigas Pablo,
Gatto Craig
Publication year - 2011
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.25.1_supplement.932.3
Subject(s) - ouabain , endoplasmic reticulum , chemistry , biophysics , electrochemical gradient , hek 293 cells , microbiology and biotechnology , nuclear membrane , membrane , biochemistry , biology , sodium , organic chemistry , gene
Na, K‐ATPase (NKA) is the integral membrane protein responsible for establishing and maintaining the Na+ electrochemical gradient across the plasma membrane of animal cells by actively exporting 3Na+ in exchange for 2K+. In this report, we present evidence suggesting that NKA builds a maintains a Na+ gradient across the nuclear envelope (NE) membrane, extending our earlier observation that NKA functions within the Endoplasmic Reticulum (Gatto et al., AJP‐cell phys., 281, C982‐C992, 2001). Immunocytochemistry of isolated nuclei from HEK‐293 cells with commercially available alpha and beta antibodies revealed that NKA was located on the nuclear envelope. In addition, membrane preparations from isolated nuclei had ouabain‐sensitive ATPase activity. Moreover, immunostaining of nuclei with antibodies against the Na/Ca‐exchanger (NCX) and NKA reveals an overlap between localization of nuclear NKA and NCX (Na/Ca‐exchanger). Given that NCX is driven by a Na+ gradient, we propose that the intracellular NKA function is utilized by NCX to extrude Ca2+ from the nucleus. We measured NKA function in isolated HEK cell nuclei via CoroNa green fluorescence. We observed an ATP‐dependent, strophanthidin‐sensitive Na accumulation in the nuclear envelope loaded with the Na‐sensitive dye. Analogous experiments are underway utilizing Ca‐sensitive probes. This work is supported by NIH grant DK083859.