Detection and processing of peripheral myelin protein PMP22 in cultured Schwann cells.
Peripheral myelin protein, 22 kDa (PMP22), is a myelin molecule associated with Schwann cells in peripheral nerves (Snipes, G. J., Suter, U., Welcher, A. A., and Shooter, E. M. (1992) J. Cell Biol. 117, 225-238). Mutations affecting the PMP22 gene have been implicated in the trembler mutation in mice (Suter, U., Welcher, A. A., Ozcelik, T., Snipes, G. J., Kosaras, B., Francke, U., Billings-Gagliardi, S., Sidman, R. L., and Shooter, E. M. (1992) Nature 356, 241-244; Suter, U., Moskow, J. J., Welcher, A. A., Snipes, G. J., Kosaras, B., Sidman, R. L., Buchberg, A. M., and Shooter, E. M. (1992) Proc. Natl. Acad. Sci. U. S. A. 89, 4382-4386) and Charcot-Marie-Tooth Disease in humans (Patel, P. I., Roa, B. B., Welcher, A. A., Schoener-Scott, R., Trask, B. J., Pentao, L., Snipes, G. J., Garcia, C. A., Francke, U., Shooter, E. M., Lupski, J. R., and Suter, U. (1992) Nature genet. 1, 159-165). In this report, we have studied PMP22 production in cultured rat Schwann cells. Schwann cells contain a 1.8-kilobase mRNA transcript coding for PMP22, and its production is up-regulated in vitro by forskolin. Metabolic labeling combined with immunoprecipitation methods using antibodies raised against synthetic peptides of PMP22 reveal that Schwann cells generate the protein from an 18-kDa precursor form which is post-translationally modified by N-linked glycosylation. A second molecule (molecular mass, 48 kDa) that reacted with PMP22 antibodies was also detected in Schwann cells but is not related chemically to PMP22 as determined by pulse-chase labeling. Metabolic labeling of rat sciatic nerve and Western blot analyses of purified rat sciatic nerve myelin reveal that deglycosylation of PMP22 gives rise to an 18-kDa protein similar in size to that in Schwann cells. These results indicate that cultured Schwann cells may provide a good model in which to investigate the production and function of PMP22 and to establish the cellular basis for the protein's involvement in inherited peripheral neuropathies.
Pareek
S
S
Montreal Neurological Institute, McGill University, Quebec, Canada.
Suter
U
U
Snipes
G J
GJ
Welcher
A A
AA
Shooter
E M
EM
Murphy
R A
RA
D000595:Amino Acid Sequence; D000818:Animals; D000831:Animals, Newborn; D001345:Autoradiography; D015153:Blotting, Western; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D007700:Kinetics; D008715:Methionine / Q000378:metabolism; D008969:Molecular Sequence Data; D009185:Myelin Proteins / Q000032:analysis / Q000096:biosynthesis*; D010455:Peptides / Q000138:chemical synthesis / Q000276:immunology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012583:Schwann Cells / Q000187:drug effects / Q000378:metabolism*; D012584:Sciatic Nerve / Q000378:metabolism*; D013462:Sulfur Radioisotopes; D013997:Time Factors; D014415:Tunicamycin / Q000494:pharmacology
D009185:Myelin Proteins; D010455:Peptides; C489546:Pmp22 protein, rat; D013462:Sulfur Radioisotopes; D014415:Tunicamycin; D005576:Colforsin; D008715:Methionine