Cytoplasmic Tail of Phospholemman Interacts with the Intracellular Loop of the Cardiac Na+/Ca2+ Exchanger

Geisinger Medical Center, Danville, Pennsylvania, United States
Journal of Biological Chemistry (Impact Factor: 4.57). 11/2006; 281(42):32004-14. DOI: 10.1074/jbc.M606876200
Source: PubMed


Phospholemman (PLM), a member of the FXYD family of small ion transport regulators, inhibits cardiac Na+/Ca2+ exchanger (NCX1). NCX1 is made up of N-terminal domain consisting of the first five transmembrane segments (residues 1-217), a large intracellular loop (residues 218-764), and a C-terminal domain comprising the last four transmembrane segments (residues 765-938). Using glutathione S-transferase (GST) pull-down assay, we demonstrated that the intracellular loop, but not the N- or C-terminal transmembrane domains of NCX1, was associated with PLM. Further analysis using protein constructs of GST fused to various segments of the intracellular loop of NCX1 suggest that PLM bound to residues 218-371 and 508-764 but not 371-508. Split Na+/Ca2+ exchangers consisting of N- or C-terminal domains with different lengths of the intracellular loop were co-expressed with PLM in HEK293 cells that are devoid of endogenous PLM and NCX1. Although expression of N-terminal but not C-terminal domain alone resulted in correct membrane targeting, co-expression of both N- and C-terminal domains was required for correct membrane targeting and functional exchange activity. NCX1 current measurements indicate that PLM decreased NCX1 current only when the split exchangers contained residues 218-358 of the intracellular loop. Co-immunoprecipitation experiments with PLM and split exchangers suggest that PLM associated with the N-terminal domain of NCX1 when it contained intracellular loop residues 218-358. TM43, a PLM mutant with its cytoplasmic tail truncated, did not co-immunoprecipitate with wild-type NCX1 when co-expressed in HEK293 cells, confirming little to no interaction between the transmembrane domains of PLM and NCX1. We conclude that PLM interacted with the intracellular loop of NCX1, most likely at residues 218-358.

Download full-text


Available from: Joseph Y Cheung,
  • Source
    • "with the NCX. The large cytosolic loop interacts with several proteins: the 14-3-3 protein, phosphorylated PLM ( phospholemman, a member of a family of transport regulators, best known as modulators of Na, K-ATPase activity) and calcineurin: they all have inhibitory function on NCX activity (Katanosaka et al. 2005; Pulina et al. 2006; Wang et al. 2006; Zhang et al. 2006). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Calcium is an ambivalent signal: it is essential for the correct functioning of cell life, but may also become dangerous to it. The plasma membrane Ca(2+) ATPase (PMCA) and the plasma membrane Na(+)/Ca(2+) exchanger (NCX) are the two mechanisms responsible for Ca(2+) extrusion. The NCX has low Ca(2+) affinity but high capacity for Ca(2+) transport, whereas the PMCA has a high Ca(2+) affinity but low transport capacity for it. Thus, traditionally, the PMCA pump has been attributed a housekeeping role in maintaining cytosolic Ca(2+), and the NCX the dynamic role of counteracting large cytosolic Ca(2+) variations (especially in excitable cells). This view of the roles of the two Ca(2+) extrusion systems has been recently revised, as the specific functional properties of the numerous PMCA isoforms and splicing variants suggests that they may have evolved to cover both the basal Ca(2+) regulation (in the 100 nM range) and the Ca(2+) transients generated by cell stimulation (in the μM range).
    Cold Spring Harbor perspectives in biology 02/2011; 3(2). DOI:10.1101/cshperspect.a004168 · 8.68 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The ability to innovate is one of the main factors that distinguish successfully led enterprises from mediocre ones. Innovation depends on the application of individual and team creativity to the task at hand. Creativity in the team depends on open communication as well as understanding of ourselves and our diversity. We present fresh insights into the essence of interpersonal communication, borrowing partly from sociobiology, a field that is not familiar to many managers. We discuss people diversity in a way that cuts through the traditional barriers of culture, race, ethnicity, language etc., based on the Myers-Briggs (Jungian) psychological typology. The influence of type on communication and teamwork is pervasive but not well understood. We then look at creativity as a process and reveal the intimate connections between this process on one hand and communication and diversity on the other. An important ingredient of effective leadership is understanding the process of creativity and learning how to overcome or by pass obstacles in its way. Embracing of these insights by the managers of technology-based enterprises leads to a more effective and satisfying teamwork and, ultimately, to better bottom-line results for the company
    Engineering Management Conference, 1994. 'Management in Transition: Engineering a Changing World', Proceedings of the 1994 IEEE International; 11/1994
  • Source

    01/2003: pages 559-575; Elsevier Science B. V..
Show more