Peripheral myelin protein 22 modulates store-operated calcium channel activity, providing insights into Charcot-Marie-Tooth disease etiology

• Published in: The Journal of biological chemistry Vol. 294; no. 32; pp. 12054 - 12065
• Main Authors: Vanoye, Carlos G., Sakakura, Masayoshi, Follis, Rose M., Trevisan, Alexandra J., Narayan, Malathi, Li, Jun, Sanders, Charles R., Carter, Bruce D.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 09.08.2019; American Society for Biochemistry and Molecular Biology
• Subjects: Animals; Calcium - metabolism; Calcium Channels - chemistry; Calcium Channels - metabolism; calcium release-activated calcium channel protein 1 (ORAI1); Charcot-Marie-Tooth disease (CMT); Charcot-Marie-Tooth Disease - metabolism; Charcot-Marie-Tooth Disease - pathology; Endoplasmic Reticulum - metabolism; endoplasmic reticulum stress (ER stress); Evoked Potentials - drug effects; Gadolinium - pharmacology; gas3; Humans; Mice; Mice, Inbred C57BL; Mice, Knockout; Mutagenesis, Site-Directed; myelin protein; Myelin Proteins - deficiency; Myelin Proteins - genetics; Myelin Proteins - metabolism; myelination; Neurobiology; neuropathy; PMP22_L16P; Schwann cells; Schwann Cells - cytology; Schwann Cells - metabolism; stromal interaction molecule 1 (STIM1); Stromal Interaction Molecule 1 - metabolism; transient receptor potential channels (TRP channels); TRPC Cation Channels - metabolism; calcium release-activated calcium channel protein 1 (ORAI1); transient receptor potential channels (TRP channels); stromal interaction molecule 1 (STIM1); Charcot-Marie-Tooth disease (CMT); PMP22_L16P; Schwann cells; myelination; endoplasmic reticulum stress (ER stress); neuropathy; gas3; myelin protein
• ISSN: 0021-9258; 1083-351X; 1083-351X
• DOI: 10.1074/jbc.RA118.006248

Charcot-Marie-Tooth (CMT) disease is a peripheral neuropathy associated with gene duplication and point mutations in the peripheral myelin protein 22 (PMP22) gene. However, the role of PMP22 in Schwann cell physiology and the mechanisms by which PMP22 mutations cause CMT are not well-understood. On the basis of homology between PMP22 and proteins associated with modulation of ion channels, we hypothesized that PMP22 alters ion channel activity. Using whole-cell electrophysiology, we show here that heterologous PMP22 expression increases the amplitude of currents similar to those ascribed to store-operated calcium (SOC) channels, particularly those involving transient receptor canonical channel 1 (TrpC1). These channels help replenish Ca2+ in the endoplasmic reticulum (ER) following stimulus-induced depletion. Currents with similar properties were recorded in WT but not pmp22−/− mouse Schwann cells. Heterologous expression of the CMT-associated PMP22_L16P variant, which fails to reach the plasma membrane and localizes to the ER, led to larger currents than WT PMP22. Similarly, Schwann cells isolated from Trembler J (TrJ; PMP22_L16P) mice had larger currents than WT littermates. Calcium imaging in live nerves and cultured Schwann cells revealed elevated intracellular Ca2+ in TrJ mice compared with WT. Moreover, we found that PMP22 co-immunoprecipitated with stromal interaction molecule 1 (STIM1), the Ca2+ sensor SOC channel subunit in the ER. These results suggest that in the ER, PMP22 interacts with STIM1 and increases Ca2+ influx through SOC channels. Excess or mutant PMP22 in the ER may elevate intracellular Ca2+ levels, which could contribute to CMT pathology.