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Journal of Biological Chemistry
Article . 2014 . Peer-reviewed
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Journal of Biological Chemistry
Article
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N-Glycosylation Is Required for Matriptase-2 Autoactivation and Ectodomain Shedding

Authors: Jiang, Jiang; Jianfeng, Yang; Ping, Feng; Bin, Zuo; Ningzheng, Dong; Qingyu, Wu; Yang, He;

N-Glycosylation Is Required for Matriptase-2 Autoactivation and Ectodomain Shedding

Abstract

Matriptase-2 is a hepatic membrane serine protease that regulates iron homeostasis. Defects in matriptase-2 cause iron deficiency anemia. In cells, matriptase-2 is synthesized as a zymogen. To date, how matriptase-2 expression and activation are regulated remains poorly understood. Here we expressed human matriptase-2 in HEK293 and hepatic BEL-7402, SMMC-7721, and QGY-7703 cells. By labeling cell surface proteins and Western analysis, we examined matriptase-2 cell surface expression, zymogen activation, and ectodomain shedding. Our results show that matriptase-2 was activated on the cell surface but not intracellularly. Activated matriptase-2 underwent ectodomain shedding, producing soluble fragments in the conditioned medium. By testing inactive mutants, R576A and S762A, we found that matriptase-2 activation and shedding were mediated by its own catalytic activity and that the one-chain form of matriptase-2 had little activity in ectodomain shedding. We made additional matriptase-2 mutants, N136Q, N184Q, N216Q, N338Q, N433Q, N453Q, and N518Q, in which each of the predicted N-glycosylation sites was mutated. All of these mutants were expressed on the cell surface. However, mutants N216Q, N453Q, and N518Q, but not the other mutants, had impaired zymogen activation and ectodomain shedding. Our results indicate that N-glycans at specific sites are critical for matriptase-2 activation. Together, these data provide new insights into the cell surface expression, zymogen activation, and ectodomain shedding of matriptase-2.

Related Organizations
Keywords

Enzyme Precursors, Glycosylation, Serine Endopeptidases, Mutation, Missense, Membrane Proteins, Gene Expression Regulation, Enzymologic, Enzyme Activation, HEK293 Cells, Amino Acid Substitution, Liver, Cell Line, Tumor, Humans

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    This is an alternative to the "Influence" indicator, which also reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
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    This indicator reflects the "current" impact/attention (the "hype") of an article in the research community at large, based on the underlying citation network.
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    This indicator reflects the initial momentum of an article directly after its publication, based on the underlying citation network.
    Top 10%
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citations
This is an alternative to the "Influence" indicator, which also reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Citations provided by BIP!
popularity
This indicator reflects the "current" impact/attention (the "hype") of an article in the research community at large, based on the underlying citation network.
BIP!Popularity provided by BIP!
influence
This indicator reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Influence provided by BIP!
impulse
This indicator reflects the initial momentum of an article directly after its publication, based on the underlying citation network.
BIP!Impulse provided by BIP!
35
Top 10%
Top 10%
Top 10%
gold