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Site-1 protease deficiency causes human skeletal dysplasia due to defective inter-organelle protein trafficking.
- Source :
-
JCI insight [JCI Insight] 2018 Jul 26; Vol. 3 (14). Date of Electronic Publication: 2018 Jul 26 (Print Publication: 2018). - Publication Year :
- 2018
-
Abstract
- Site-1 protease (S1P), encoded by MBTPS1, is a serine protease in the Golgi. S1P regulates lipogenesis, endoplasmic reticulum (ER) function, and lysosome biogenesis in mice and in cultured cells. However, how S1P differentially regulates these diverse functions in humans has been unclear. In addition, no human disease with S1P deficiency has been identified. Here, we report a pediatric patient with an amorphic and a severely hypomorphic mutation in MBTPS1. The unique combination of these mutations results in a frequency of functional MBTPS1 transcripts of approximately 1%, a finding that is associated with skeletal dysplasia and elevated blood lysosomal enzymes. We found that the residually expressed S1P is sufficient for lipid homeostasis but not for ER and lysosomal functions, especially in chondrocytes. The defective S1P function specifically impairs activation of the ER stress transducer BBF2H7, leading to ER retention of collagen in chondrocytes. S1P deficiency also causes abnormal secretion of lysosomal enzymes due to partial impairment of mannose-6-phosphate-dependent delivery to lysosomes. Collectively, these abnormalities lead to apoptosis of chondrocytes and lysosomal enzyme-mediated degradation of the bone matrix. Correction of an MBTPS1 variant or reduction of ER stress mitigated collagen-trafficking defects. These results define a new congenital human skeletal disorder and, more importantly, reveal that S1P is particularly required for skeletal development in humans. Our findings may also lead to new therapies for other genetic skeletal diseases, as ER dysfunction is common in these disorders.
- Subjects :
- Apoptosis
Basic-Leucine Zipper Transcription Factors metabolism
Bone Diseases, Developmental physiopathology
Cell Culture Techniques
Child, Preschool
Chondrocytes metabolism
Collagen metabolism
Endoplasmic Reticulum metabolism
Female
Gene Knockdown Techniques
Genetic Diseases, Inborn
Golgi Apparatus metabolism
Homeostasis
Humans
Lipogenesis
Lysosomes metabolism
Mannosephosphates
Mutation
Bone Diseases, Developmental genetics
Bone Diseases, Developmental metabolism
Proprotein Convertases genetics
Proprotein Convertases metabolism
Protein Transport
Serine Endopeptidases genetics
Serine Endopeptidases metabolism
Subjects
Details
- Language :
- English
- ISSN :
- 2379-3708
- Volume :
- 3
- Issue :
- 14
- Database :
- MEDLINE
- Journal :
- JCI insight
- Publication Type :
- Academic Journal
- Accession number :
- 30046013
- Full Text :
- https://doi.org/10.1172/jci.insight.121596