Transmembrane segments prevent surface expression of sodium channel Nav1.8 and promote calnexin-dependent channel degradation.
The voltage-gated sodium channel (Na(v)) 1.8 contributes substantially to the rising phase of action potential in small dorsal root ganglion neurons. Na(v)1.8 is majorly localized intracellularly and its expression on the plasma membrane is regulated by exit from the endoplasmic reticulum (ER). Previous work has identified an ER-retention/retrieval motif in the first intracellular loop of Na(v)1.8, which prevents its surface expression. Here we report that the transmembrane segments of Na(v)1.8 also cause this channel retained in the ER. Using transferrin receptor and CD8α as model molecules, immunocytochemistry showed that the first, second, and third transmembrane segments in each domain of Na(v)1.8 reduced their surface expression. Alanine-scanning analysis revealed acidic amino acids as critical factors in the odd transmembrane segments. Furthermore, co-immunoprecipitation experiments showed that calnexin interacted with acidic amino acid-containing sequences through its transmembrane segment. Overexpression of calnexin resulted in increased degradation of those proteins through the ER-associated degradation pathway, whereas down-regulation of calnexin reversed the phenotype. Thus our results reveal a critical role and mechanism of transmembrane segments in surface expression and degradation of Na(v)1.8.
Li
Qian
Q
From the Laboratory of Molecular Cell Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China.
Su
Yuan-Yuan
YY
From the Laboratory of Molecular Cell Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China.
Wang
Hao
H
From the Laboratory of Molecular Cell Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China.
Li
Lei
L
From the Laboratory of Molecular Cell Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China.
Wang
Qiong
Q
From the Laboratory of Molecular Cell Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China.
Bao
Lan
L
From the Laboratory of Molecular Cell Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China. Electronic address: baolan@sibs.ac.cn.
D020816:Amino Acid Motifs; D000818:Animals; D019556:COS Cells; D037281:Calnexin / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000235:genetics / Q000378:metabolism*; D002522:Chlorocebus aethiops; D004721:Endoplasmic Reticulum / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000502:physiology*; D006801:Humans; D008297:Male; D062559:NAV1.8 Voltage-Gated Sodium Channel; D017434:Protein Structure, Tertiary; D051381:Rats; D017207:Rats, Sprague-Dawley; D015222:Sodium Channels / Q000096:biosynthesis* / Q000235:genetics
D062559:NAV1.8 Voltage-Gated Sodium Channel; C568317:SCN10A protein, human; C568319:Scn10a protein, rat; D015222:Sodium Channels; D037281:Calnexin