Direct relationship between increased expression and mistrafficking of the Charcot–Marie–Tooth–associated protein PMP22

• Published in: The Journal of biological chemistry Vol. 295; no. 34; pp. 11963 - 11970
• Main Authors: Marinko, Justin T., Carter, Bruce D., Sanders, Charles R.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 21-08-2020; American Society for Biochemistry and Molecular Biology
• Subjects: cell surface protein; Charcot-Marie-Tooth Disease - genetics; Charcot-Marie-Tooth Disease - metabolism; Charcot-Marie-Tooth Disease - pathology; Charcot–Marie–Tooth disease (CMT); Editors' Picks; flow cytometry; Gene Expression Regulation; HEK293 Cells; Humans; membrane protein; membrane trafficking; myelin; Myelin Proteins - biosynthesis; Myelin Proteins - genetics; peripheral neuropathy; Protein Aggregation, Pathological - genetics; Protein Aggregation, Pathological - metabolism; Protein Aggregation, Pathological - pathology; protein folding; protein misfolding; Protein Transport; myelin; cell surface protein; Charcot–Marie–Tooth disease (CMT); protein misfolding; membrane protein; protein folding; flow cytometry; peripheral neuropathy; membrane trafficking
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.AC120.014940

Charcot–Marie–Tooth disease (CMT) is a neuropathy of the peripheral nervous system that afflicts ∼1:2500 people. The most common form of this disease (CMT1A, 1:4000) is associated with duplication of chromosome fragment 17p11.2-12, which results in a third WT PMP22 allele. In rodent models overexpressing the PMP22 (peripheral myelin protein 22) protein and in dermal fibroblasts from patients with CMT1A, PMP22 aggregates have been observed. This suggests that overexpression of PMP22 under CMT1A conditions overwhelms the endoplasmic reticulum quality control system, leading to formation of cytotoxic aggregates. In this work, we used a single-cell flow-cytometry trafficking assay to quantitatively examine the relationship between PMP22 expression and trafficking efficiency in individual cells. We observed that as expression of WT or disease variants of PMP22 is increased, the amount of intracellular PMP22 increases to a greater extent than the amount of surface-trafficked protein. This was true for both transiently transfected cells and PMP22 stable expressing cells. Our results support the notion that overexpression of PMP22 in CMT1A leads to a disproportionate increase in misfolding and mistrafficking of PMP22, which is likely a contributor to disease pathology and progression.