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Disrupting the transmembrane domain interface between PMP22 and MPZ causes peripheral neuropathy
Natalya Pashkova1, Tabitha A Peterson1, Christopher P Ptak2
1Department of Molecular Physiology and Biophysics, Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA.
Abstract:
Peripheral Myelin Protein 22 (PMP22) and MPZ are abundant myelin membrane proteins in Schwann cells. The MPZ adhesion protein holds myelin wraps together across the intraperiod line. PMP22 is a tetraspan protein belonging to the Claudin superfamily. Loss of either MPZ or PMP22 causes severe demyelinating Charcot-Marie-Tooth (CMT) peripheral neuropathy, and duplication of PMP22 causes the most common form of CMT, CMT1A. Yet, the molecular functions provided by PMP22 and how its alteration causes CMT are unknown. Here, we find MPZ and PMP22 form a specific complex through interfaces within their transmembrane domains. We also find that the PMP22 A67T patient variant that causes a loss-of-function (hereditary neuropathy with pressure palsies) phenotype maps to this interface, and blocks MPZ association without affecting localization to the plasma membrane or interactions with other proteins. These data define the molecular basis for the MPZ ∼ PMP22 interaction and indicate this complex fulfills an important function in myelinating cells.
Insights
Peripheral myelin protein 22 (PMP22) and MPZ form a complex crucial for myelin. A PMP22 variant disrupts this interaction, revealing the molecular basis of related neuropathies like Charcot-Marie-Tooth disease.
Area of Science:
- Neuroscience
- Molecular Biology
- Genetics
Background:
- Peripheral myelin protein 22 (PMP22) and MPZ are key Schwann cell myelin proteins.
- Alterations in PMP22 and MPZ cause demyelinating peripheral neuropathies, including Charcot-Marie-Tooth disease (CMT).
- The precise molecular functions of PMP22 and mechanisms underlying CMT remain unclear.
Purpose of the Study:
- To elucidate the molecular interaction between PMP22 and MPZ.
- To investigate the functional consequences of PMP22 mutations on this interaction.
- To define the structural basis of PMP22-MPZ complex formation.
Main Methods:
- Co-immunoprecipitation assays to detect protein complex formation.
- Analysis of PMP22 variants, including the A67T mutation, using cell-based assays.
- Cellular localization studies to assess protein trafficking and membrane association.
Main Results:
- MPZ and PMP22 form a specific complex mediated by their transmembrane domains.
- The PMP22 A67T patient variant, associated with hereditary neuropathy with pressure palsies, disrupts MPZ binding.
- This PMP22 variant does not affect its plasma membrane localization or interactions with other proteins.
Conclusions:
- The MPZ-PMP22 complex is formed through specific interfaces within their transmembrane regions.
- Disruption of the MPZ-PMP22 interaction by PMP22 variants underlies certain peripheral neuropathies.
- This interaction is critical for normal myelin function in Schwann cells.
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