Mutation of Amino Acid Residues in the Putative Transmembrane Segments of the Cardiac Sarcolemmal Na+-Ca2+ Exchanger

Nicoll, Debora A.; Hryshko, Larry V.; Matsuoka, Satoshi; Frank, Joy S.; Philipson, Kenneth D.

doi:10.1074/jbc.271.23.13385

Cited by 136 publications

(158 citation statements)

References 34 publications

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“…As two sodium ions are translocated together with one bile acid molecule via NTCP and ASBT, this transport is electrogenic Weinman 1997;Weinman et al 1998). As reported for other sodium-coupled cotransporters and exchangers (Nicoll et al 1996;Jung 2001;Murtazina et al 2001), negatively charged amino acids at the outer surface of the carrier protein are potential binding sites for cationic sodium ions. To address this question for rat Ntcp, a series of aspartate-asparagine and glutamateglutamine mutations were screened for transport function and membrane expression in our group (Zahner et al 2003).…”

Section: Structure-activity Relationships Of the Slc10 Membersmentioning

confidence: 80%

The solute carrier family SLC10: more than a family of bile acid transporters regarding function and phylogenetic relationships

Geyer

Wilke

Petzinger

2006

Naunyn Schmied Arch Pharmacol

161

138

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The solute carrier family 10 (SLC10) comprises two sodium-dependent bile acid transporters, i.e. the Na + / taurocholate cotransporting polypeptide (NTCP; SLC10A1) and the apical sodium-dependent bile acid transporter (ASBT; SLC10A2). These carriers are essentially involved in the maintenance of the enterohepatic circulation of bile acids mediating the first step of active bile acid transport through the membrane barriers in the liver (NTCP) and intestine (ASBT). Recently, four new members of the SLC10 family were described and referred to as P3 (SLC10A3), P4 (SLC10A4), P5 (SLC10A5) and sodium-dependent organic anion transporter (SOAT; SLC10A6). Experimental data supporting carrier function of P3, P4, and P5 is currently not available. However, as demonstrated for SOAT, not all members of the SLC10 family are bile acid transporters. SOAT specifically transports steroid sulfates such as oestrone-3-sulfate and dehydroepiandrosterone sulfate in a sodium-dependent manner, and is considered to play an important role for the cellular delivery of these prohormones in testes, placenta, adrenal gland and probably other peripheral tissues. ASBT and SOAT are the most homologous members of the SLC10 family, with high sequence similarity (∼70%) and almost identical gene structures. Phylogenetic analyses of the SLC10 family revealed that ASBT and SOAT genes emerged from a common ancestor gene. Structure-activity relationships of NTCP, ASBT and SOAT are discussed at the amino acid sequence level.Based on the high structural homology between ASBT and SOAT, pharmacological inhibitors of the ASBT, which are currently being tested in clinical trials for cholesterollowering therapy, should be evaluated for their crossreactivity with SOAT.

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Section: Structure-activity Relationships Of the Slc10 Membersmentioning

confidence: 80%

The solute carrier family SLC10: more than a family of bile acid transporters regarding function and phylogenetic relationships

Geyer

Wilke

Petzinger

2006

Naunyn Schmied Arch Pharmacol

161

138

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“…Previous studies with the cardiac Na ϩ /Ca 2ϩ exchanger, NCX1, had implicated the so-called ␣-repeat regions of the molecule in forming the binding pocket for ion translocation (45,46). Functional studies on a deletion mutant of bovine NCKX1 and a C. elegans paralog (cNCKX) have suggested similar regions also specify the transport sites needed for K ϩ -dependent Na ϩ /Ca 2ϩ exchangers (30).…”

Section: Discussionmentioning

confidence: 99%

Molecular Cloning of a Third Member of the Potassium-dependent Sodium-Calcium Exchanger Gene Family,NCKX3

Kraev

Lytton

2001

Journal of Biological Chemistry

Self Cite

116

143

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We describe here the identification and characterization of a novel member of the family of K ؉ -dependent Na ؉ /Ca 2؉ exchangers, NCKX3 (gene SLC24A3). Human NCKX3 encodes a protein of 644 amino acids that displayed a high level of sequence identity to the other family members, rod NCKX1 and cone/neuronal NCKX2, in the hydrophobic regions surrounding the "␣ -repeat" sequences thought to form the ion-binding pocket for transport. Outside of these regions NCKX3 showed no significant identity to other known proteins. As anticipated from this sequence similarity, NCKX3 displayed K ؉ -dependent Na ؉ /Ca 2؉ exchanger activity when assayed in heterologous expression systems, using digital imaging of fura-2 fluorescence, electrophysiology, or radioactive 45 Ca 2؉ uptake. The N-terminal region of NCKX3, although not essential for expression, increased functional activity at least 10-fold and may represent a cleavable signal sequence. NCKX3 transcripts were most abundant in brain, with highest levels found in selected thalamic nuclei, in hippocampal CA1 neurons, and in layer IV of the cerebral cortex. Many other tissues also expressed NCKX3 at lower levels, especially aorta, uterus, and intestine, which are rich in smooth muscle. The discovery of NCKX3 thus expands the K ؉ -dependent Na ؉ /Ca 2؉ exchanger family and suggests this class of transporter has a more widespread role in cellular Ca 2؉ handling than previously appreciated.

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“…The mammalian Na ϩ /Ca 2ϩ exchanger forms a multigene family comprising three isoforms, NCX1, NCX2, and NCX3, which share ϳ70% identity in the overall amino acid sequences (2)(3)(4). On the basis of the hydropathy analysis, the mature Na ϩ /Ca 2ϩ exchanger proteins were modeled to consist of 11 TMs 1 and a large central hydrophilic loop between TM5 and TM6, with the N terminus localized on the extracellular side and the C terminus and the large central loop being on the intracellular side of the membrane (4,5). Recent studies on the topology of the NCX1 polypeptide have produced data that are consistent with the N-terminal half of the 11 TM model (6 -10), but these data do not support the C-terminal half of the model (9, 10), indicating that the model requires revision.…”

Section: Externally Applied Nimentioning

confidence: 99%

Chimeric Analysis of Na+/Ca2+ Exchangers NCX1 and NCX3 Reveals Structural Domains Important for Differential Sensitivity to External Ni2+ or Li+

Iwamoto¹,

Uehara²,

Nakamura³

et al. 1999

Journal of Biological Chemistry

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Externally applied Ni2؉ , which apparently competes with Ca 2؉ in all three isoforms of Na ؉ /Ca 2؉ exchanger, inhibits exchange activity of NCX1 or NCX2 with a 10-fold higher affinity than that of NCX3, whereas stimulation of exchange by external Li ؉ is significantly greater in NCX2 and NCX3 than in NCX1 (Iwamoto, T., and Shigekawa, M. (1998) Am. J. Physiol. 275, C423-C430). Here we identified structural domains in the exchanger that confer differential sensitivity to Ni 2؉ or Li ؉ by measuring intracellular Na ؉ -dependent 45 Ca 2؉ uptake in CCL39 cells stably expressing NCX1/NCX3 chimeras or mutants. We found that two segments in the exchanger corresponding mostly to the internal ␣-1 and ␣-2 repeats are individually responsible for the alteration of Ni 2؉ sensitivity, both together accounting for ϳ80% of the difference between NCX1 and NCX3. In contrast, the segment corresponding to the ␣-2 repeat fully accounts for the differential Li ؉ sensitivity between the isoforms. The Ni 2؉ sensitivity was mimicked, respectively, by simultaneous substitution of two amino acids in the ␣-1 repeat (N125G/T127I in NCX1 and G159N/I161T in NCX3) and substitution of one amino acid in the ␣-2 repeat (V820A in NCX1 and A809V in NCX3). On the other hand, the Li ؉ sensitivity was mimicked by double substitution mutation in the ␣-2 repeat (V820A/Q826V in NCX1 and A809V/V815Q in NCX3). Single substitution mutations at Asn 125 and Val 820 of NCX1 caused significant alterations in the interactions of the exchanger with Ca 2؉ and Ni 2؉ , and Ni 2؉ and Li ؉ , respectively, although the extent of alteration varied depending on the nature of side chains of substituted residues. Since the above four important residues are mostly in the putative loops of the ␣ repeats, these regions might form an ion interaction domain in the exchanger.

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Mutation of Amino Acid Residues in the Putative Transmembrane Segments of the Cardiac Sarcolemmal Na+-Ca2+ Exchanger

Cited by 136 publications

References 34 publications

The solute carrier family SLC10: more than a family of bile acid transporters regarding function and phylogenetic relationships

The solute carrier family SLC10: more than a family of bile acid transporters regarding function and phylogenetic relationships

Molecular Cloning of a Third Member of the Potassium-dependent Sodium-Calcium Exchanger Gene Family,NCKX3

Chimeric Analysis of Na+/Ca2+ Exchangers NCX1 and NCX3 Reveals Structural Domains Important for Differential Sensitivity to External Ni2+ or Li+

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