Journal
JOURNAL OF BIOLOGICAL CHEMISTRY
Volume 293, Issue 21, Pages 8113-8127Publisher
AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
DOI: 10.1074/jbc.RA117.001503
Keywords
matrix metalloproteinase (MMP); mesenchymal stem cells (MSCs); collagen; fibroblast; intracellular trafficking; MT1-MMP; type I collagen; hemopexin domain
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Funding
- National Institutes of Health [AR065524, CA071699, HL071818, HL122416]
- Breast Cancer Research Foundation
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Following ENU mutagenesis, a phenodeviant line was generated, termed the Cartoon mouse, that exhibits profound defects in growth and development. Cartoon mice harbor a single S466P point mutation in the MT1-MMP hemopexin domain, a 200-amino acid segment that is thought to play a critical role in regulating MT1-MMP collagenolytic activity. Herein, we demonstrate that the MT1-MMPS466P mutation replicates the phenotypic status of Mt1-mmp-null animals as well as the functional characteristics of MT1-MMP-/- cells. However, rather than a loss-of-function mutation acquired as a consequence of defects in MT1-MMP proteolytic activity, the S466P substitution generates a misfolded, temperature-sensitive mutant that is abnormally retained in the endoplasmic reticulum (ER). By contrast, the WT hemopexin domain does not play a required role in regulating MT1-MMP trafficking, as a hemopexin domain-deletion mutant is successfully mobilized to the cell surface and displays nearly normal collagenolytic activity. Alternatively, when MT1-MMPS466P-expressing cells are cultured at a permissive temperature of 25 degrees C that depresses misfolding, the mutant successfully traffics from the ER to the trans-Golgi network (ER trans-Golgi network), where it undergoes processing to its mature form, mobilizes to the cell surface, and expresses type I collagenolytic activity. Together, these analyses define the Cartoon mouse as an unexpected gain-of-abnormal function mutation, wherein the temperature-sensitive mutant phenocopies MT1-MMP-/- mice as a consequence of eliciting a specific ER trans-Golgi network trafficking defect.
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