期刊
JOURNAL OF BIOLOGICAL CHEMISTRY
卷 288, 期 51, 页码 36409-36417出版社
AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
DOI: 10.1074/jbc.M113.530584
关键词
Calcium Signaling; Glycoprotein; Ion Channels; Protein Stability; TRP Channels
资金
- National Institutes of Health from the NINDS [NS060801, NS061808, NS061934, NS072501]
- National Institutes of Health from the NHLBI [HL082517]
- Department of Veterans Affairs (Baltimore)
Background:N-Glycosylation is important for the function and regulation of ion channels but has not been examined for Trpm4. Results:N-Glycosylation is not required for surface expression, but complex N-glycosylation stabilizes Trpm4b surface expression. Conclusion: Complex N-glycosylation of Trpm4b has important functional implications. Significance: By promoting surface expression, N-glycosylation contributes importantly to calcium regulation byTrpm4b. N-Glycosylation is important for the function and regulation of ion channels. We examined the role of N-glycosylation of transient receptor potential melastatin (Trpm) 4b, a membrane glycoprotein that regulates calcium influx. Trpm4b was expressed in vivo in all rat tissues examined. In each tissue, Trpm4b had a different molecular mass, between approximate to 129 and approximate to 141 kDa, but all reverted to approximate to 120 kDa following treatment with peptide:N-glycosidase F, consistent with N-glycosylation being the principal form of post-translational modification of Trpm4b in vivo. In six stable isogenic cell lines that express different levels of Trpm4b, two forms were found, high mannose, core-glycosylated and complex, highly glycosylated (HG), with HG-Trpm4b comprising 85% of the total Trpm4b expressed. For both forms, surface expression was directly proportional to the total Trpm4b expressed. Complex N-glycosylation doubled the percentage of Trpm4b at the surface, compared with high mannose N-glycosylation. Mutation of the single N-glycosylation consensus sequence at Asn-988 (Trpm4b-N988Q), located near the pore-forming loop between transmembrane helices 5 and 6, prevented glycosylation, but did not prevent surface expression, impair formation of functional membrane channels, or alter channel conductance. In transfection experiments, the time courses for appearance of HG-Trpm4b and Trpm4b-N988Q on the surface were similar. In experiments with cycloheximide inhibition of protein synthesis, the time course for disappearance of HG-Trpm4b from the surface was much slower than that for Trpm4b-N988Q. We conclude that N-glycosylation is not required for surface expression or channel function, but that complex N-glycosylation plays a crucial role in stabilizing surface expression of Trpm4b.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据