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A novel human mutation in the SLC9A1 gene results in abolition of Na+/H+ exchanger activity.

Li X, Fliegel L - PLoS ONE (2015)

Bottom Line: We examined the effect of this mutation on expression, targeting and activity of the Na+/H+ exchanger.Targeting of the mutant protein to the cell surface was normal and expression levels were only slightly reduced relative to the wild type protein.A histidine residue at this location may disrupt the cation binding site or the pore of the Na+/H+ exchanger protein.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada.

ABSTRACT
The SLC9A1 gene, the Na+/H+ exchanger isoform 1 is the principal plasma membrane Na+/H+ exchanger of mammalian cells and functions by exchanging one intracellular proton for one extracellular sodium. The human protein is 815 amino acids in length. Five hundred N-terminal amino acids make up the transport domain of the protein and are believed to form 12 transmembrane segments. Recently, a genetic mutation of the Na+/H+ exchanger isoform 1, N266H, was discovered in a human patient through exome sequencing. We examined the effect of this mutation on expression, targeting and activity of the Na+/H+ exchanger. Mutant N266H protein was expressed in AP-1 cells, which lack their endogenous Na+/H+ exchanger protein. Targeting of the mutant protein to the cell surface was normal and expression levels were only slightly reduced relative to the wild type protein. However, the N266H mutant protein had no detectable Na+/H+ exchanger activity. A histidine residue at this location may disrupt the cation binding site or the pore of the Na+/H+ exchanger protein.

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Molecular model of N266 within the NHE1 protein.Position of N266 within the molecular model of NHE1 proposed by Landau et al. [16]. TM VII of NHE1 (amino acids 254–277) are highlighted in blue, N266 and its side chain are shown in red. The side chain of amino acid T197 of TM V is shown in yellow. Ser235 of the extended region of TM IV is indicated by magenta color. A, side view through the membrane. B, enlarged view from side and top of the membrane.
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pone.0119453.g003: Molecular model of N266 within the NHE1 protein.Position of N266 within the molecular model of NHE1 proposed by Landau et al. [16]. TM VII of NHE1 (amino acids 254–277) are highlighted in blue, N266 and its side chain are shown in red. The side chain of amino acid T197 of TM V is shown in yellow. Ser235 of the extended region of TM IV is indicated by magenta color. A, side view through the membrane. B, enlarged view from side and top of the membrane.

Mentions: To gather insights into the mechanism by which the mutation N266H could cause a defect in NHE1 activity we examined the structure of NHE1. While the complete structure of NHE1 has not been deduced, a model of NHE1 has been elucidated [16]. Fig. 3 illustrates this model. The amino acid N266 is present in TM VII of the protein, approximately mid level within the membrane. The side chair of N266 extends partially towards TM V (Fig. 3B) but also points towards the extended region of TM IV, which is thought to be part of the critical fold of NHE1 important in transport.


A novel human mutation in the SLC9A1 gene results in abolition of Na+/H+ exchanger activity.

Li X, Fliegel L - PLoS ONE (2015)

Molecular model of N266 within the NHE1 protein.Position of N266 within the molecular model of NHE1 proposed by Landau et al. [16]. TM VII of NHE1 (amino acids 254–277) are highlighted in blue, N266 and its side chain are shown in red. The side chain of amino acid T197 of TM V is shown in yellow. Ser235 of the extended region of TM IV is indicated by magenta color. A, side view through the membrane. B, enlarged view from side and top of the membrane.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4356549&req=5

pone.0119453.g003: Molecular model of N266 within the NHE1 protein.Position of N266 within the molecular model of NHE1 proposed by Landau et al. [16]. TM VII of NHE1 (amino acids 254–277) are highlighted in blue, N266 and its side chain are shown in red. The side chain of amino acid T197 of TM V is shown in yellow. Ser235 of the extended region of TM IV is indicated by magenta color. A, side view through the membrane. B, enlarged view from side and top of the membrane.
Mentions: To gather insights into the mechanism by which the mutation N266H could cause a defect in NHE1 activity we examined the structure of NHE1. While the complete structure of NHE1 has not been deduced, a model of NHE1 has been elucidated [16]. Fig. 3 illustrates this model. The amino acid N266 is present in TM VII of the protein, approximately mid level within the membrane. The side chair of N266 extends partially towards TM V (Fig. 3B) but also points towards the extended region of TM IV, which is thought to be part of the critical fold of NHE1 important in transport.

Bottom Line: We examined the effect of this mutation on expression, targeting and activity of the Na+/H+ exchanger.Targeting of the mutant protein to the cell surface was normal and expression levels were only slightly reduced relative to the wild type protein.A histidine residue at this location may disrupt the cation binding site or the pore of the Na+/H+ exchanger protein.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada.

ABSTRACT
The SLC9A1 gene, the Na+/H+ exchanger isoform 1 is the principal plasma membrane Na+/H+ exchanger of mammalian cells and functions by exchanging one intracellular proton for one extracellular sodium. The human protein is 815 amino acids in length. Five hundred N-terminal amino acids make up the transport domain of the protein and are believed to form 12 transmembrane segments. Recently, a genetic mutation of the Na+/H+ exchanger isoform 1, N266H, was discovered in a human patient through exome sequencing. We examined the effect of this mutation on expression, targeting and activity of the Na+/H+ exchanger. Mutant N266H protein was expressed in AP-1 cells, which lack their endogenous Na+/H+ exchanger protein. Targeting of the mutant protein to the cell surface was normal and expression levels were only slightly reduced relative to the wild type protein. However, the N266H mutant protein had no detectable Na+/H+ exchanger activity. A histidine residue at this location may disrupt the cation binding site or the pore of the Na+/H+ exchanger protein.

Show MeSH