Peripheral myelin protein 22 kDa and protein zero: domain specific trans-interactions
Introduction
The myelin sheath of peripheral nervous system (PNS) is generated by Schwann cells, from which the myelin radiates and wraps around adjacent axons (Arroyo and Scherer, 2000). Peripheral myelination requires the synthesis of large quantities of membrane lipids and a specific set of proteins that play key roles in the structure and function of the myelin sheath. Two important molecules of peripheral myelin are the protein zero (P0), which makes up approximately 50% of all myelin proteins (Greenfield et al., 1973), and the peripheral myelin protein 22 kDa (PMP22), which comprises 2–5% of total PNS myelin (Pareek et al., 1993).
The genes encoding P0 and PMP22 have been well characterized, and numerous mutations associated with these genes have been identified in hereditary demyelinating peripheral neuropathies in mice and human, such as Charcot–Marie–Tooth disease (CMT), Dejerine–Sottas Syndrome (DSS), Congenital Hypomyelination (CH) and Hereditary Neuropathy with Pressure Palsies (HNPP), respectively (for review, see De Jonghe et al., 1997, Müller, 2000, Suter and Snipes, 1995). Genotype–phenotype correlations revealed that different mutations cause phenotypes with varying degrees of disease severity (De Jonghe et al., 1997, Nelis et al., 1999, Warner et al., 1996). Furthermore, duplication and deletion of the PMP22 gene is associated with CMT1A and HNPP, respectively, indicating that a gene dosage effect is involved in the pathological mechanism (Patel and Lupski, 1994). Mutations, gene duplication or gene deletion could lead to a nonfunctional protein or interfere with the stoichiometry of protein–protein interactions and ultimately to an unstable myelin structure. PMP22 seems to form heterophilic complexes with P0 in peripheral myelin as well as in ovary carcinoma cells expressing both proteins (D'Urso et al., 1999). Furthermore, PMP22 protein carrying CMT1A-related point mutations accumulates in the ER/Golgi compartments thereby causing a dominant negative effect on the intracellular trafficking of the wild-type PMP22 from the unaffected allele (D'Urso et al., 1998, Naef and Suter, 1999, Naef et al., 1997, Notterpek et al., 1997, Tobler et al., 1999).
It has been speculated that the heterophilic interaction of PMP22 and P0 may be important for a function of these proteins in maintenance and stability of PNS myelin (D'Urso et al., 1999, Scherer and Arroyo, 2002). To evaluate the mechanism of the heterophilic PMP22 and P0 interaction, we have generated a cell adhesion assay with retrovirally transduced HeLa cells expressing PMP22 or P0, respectively, and confirmed the results in GST pull down studies. These data indicate that PMP22 and P0 perform homophilic and heterophilic interactions. Mutations located in distinct regions of the extracellular domain of P0 protein that are associated with CMT1 and DSS disease clearly impair those interactions.
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Generation of HeLa cell pools expressing P0, PMP22 and Plasmolipin
To elucidate the interaction of PMP22 and P0 proteins, we transduced HeLa cells with retroviral constructs encoding PMP22, P0 and Plasmolipin (PLA), respectively. Expression of the constructs in G418 resistant cells was confirmed by reverse transcription (RT)-PCR using construct-specific primers (data not shown) and by Western blotting (Fig. 1). To ensure that each protein was ectopically expressed and inserted into the plasma membrane, intact cells were prelabelled by membrane impermeable
Discussion
The molecular mechanisms of membrane assembly and compaction of the multilamellar structure of myelin sheaths is still not well understood. Previous studies have identified P0 as a transmembrane protein with homophilic adhesion capacity (D'Urso et al., 1990, D'Urso et al., 1999, Filbin et al., 1990, Schneider-Schaulies et al., 1990) and, based on crystallography studies it has been suggested that P0 forms interdigitating homotetramers in cis and trans configuration in myelin membranes (Inouye
Antibodies
The following antibodies were used as indicated: Polyclonal anti-PMP22 antibody (1:300; Antibody Service, Dr. Pineda, Berlin, Germany), polyclonal anti-P0 antibody (1:500; Hasse et al., 2002), polyclonal anti-Plasmolipin antibody (1:200; Hamacher et al., 2001) and monoclonal anti-Glutathione-S-Transferase antibody (1:2000; Amersham Pharmacia Biotechnology, Buckinghamshire, UK).
Retroviral overexpression of PMP22, P0 and Plasmolipin in vitro
The open reading frames (ORFs) of rat PMP22 (NM017037), rat P0 (K03242, BF562392) and rat Plasmolipin (PLA, NM022533)
Acknowledgments
This work was supported in part by the Deutsche Forschungsgemeinschaft (Mu630/5-4), the Elterninitiative Kinderkrebsklinik and a Grant from the Medical Faculty of the University of Düsseldorf.
References (37)
- et al.
The cytoplasmic domain of myelin glycoprotein P0 interacts with negatively charged phospholipid bilayers
J. Biol. Chem.
(1994) - et al.
Protein zero of peripheral nerve myelin: biosynthesis, membrane insertion, and evidence for homotypic interaction
Neuron
(1990) - et al.
The role of complex carbohydrates in adhesion of the myelin protein Po
Neuron
(1991) - et al.
3rd Workshop of the European CMT consortium: 54th ENMC International Workshop on Genotype/Phenotype Correlations in Charcot–Marie–Tooth Type 1 and Hereditary Neuropathy with Liability to Pressure Palsies 28–30 November 1997, Naarden, The Netherlands
Neuromuscular Disord.
(1998) - et al.
Phenotypic correction of primary Fanconi anemia T cells with retroviral vectors as a diagnostic tool
Exp. Hematol.
(2002) - et al.
Tetrameric assembly of full-sequence protein zero myelin glycoprotein by synchrotron x-ray scattering
Biophys. J.
(1999) - et al.
Impaired intracellular trafficking is a common disease mechanism of PMP22 point mutations in peripheral neuropathies
Neurobiol. Dis.
(1999) - et al.
Aberrant protein trafficking in Trembler suggests a disease mechanism for hereditary human peripheral neuropathies
Mol. Cell. Neurosci.
(1997) - et al.
Detection and processing of peripheral myelin protein PMP22 in cultured Schwann cells
J. Biol. Chem.
(1993) - et al.
Charcot–Marie–Tooth disease: a new paradigm for the mechanism of inherited disease
Trends Genet.
(1994)
Crystal structure of the extracellular domain from P0, the major structural protein of peripheral nerve myelin
Neuron
On the molecular architecture of myelinated fibers
Histochem. Cell Biol.
Charcot–Marie–Tooth disease and related peripheral neuropathies
J. Peripher. Nerv. Syst.
Overloaded endoplasmic reticulum–Golgi compartments, a possible pathomechanism of peripheral neuropathies caused by mutations of the peripheral myelin protein PMP22
J. Neurosci.
Peripheral myelin protein 22 and protein zero: a novel association in peripheral nervous system myelin
J. Neurosci.
Homophilic adhesion of the myelin Po protein requires glycosylation of both molecules in the homophilic pair
J. Cell Biol.
The Ig-disulfide bond of myelin Po protein is essential to its adhesion
J. Neurochem.
Role of myelin P0 protein as a homophilic adhesion molecule
Nature
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These authors contributed equally to this study.