Molecular cloning of plasmolipin. Characterization of a novel proteolipid restricted to brain and kidney

The MAL Family of Proteins: Normal Function, Expression in Cancer, and Potential Use as Cancer Biomarkers

The MAL family of integral membrane proteins consists of MAL, MAL2, MALL, PLLP, CMTM8, MYADM, and MYADML2. The best characterized members are elements of the machinery that controls specialized pathways of membrane traffic and cell signaling. This review aims to help answer the following questions about the MAL-family genes: (i) is their expression regulated in cancer and, if so, how? (ii) What role do they play in cancer? (iii) Might they have biomedical applications? Analysis of large-scale gene expression datasets indicated altered levels of MAL-family transcripts in specific cancer types. A comprehensive literature search provides evidence of MAL-family gene dysregulation and protein function repurposing in cancer. For MAL, and probably for other genes of the family, dysregulation is primarily a consequence of gene methylation, although copy number alterations also contribute to varying degrees. The scrutiny of the two sources of information, datasets and published studies, reveals potential prognostic applications of MAL-family members as cancer biomarkers-for instance, MAL2 in breast cancer, MAL2 and MALL in pancreatic cancer, and MAL and MYADM in lung cancer-and other biomedical uses. The availability of validated antibodies to some MAL-family proteins sanctions their use as cancer biomarkers in routine clinical practice.

MALL, a membrane-tetra-spanning proteolipid overexpressed in cancer, is present in membraneless nuclear biomolecular condensates

Proteolipids are proteins with unusual lipid-like properties. It has long been established that PLP and plasmolipin, which are two unrelated membrane-tetra-spanning myelin proteolipids, can be converted in vitro into a water-soluble form with a distinct conformation, raising the question of whether these, or other similar proteolipids, can adopt two different conformations in the cell to adapt their structure to distinct environments. Here, we show that MALL, another proteolipid with a membrane-tetra-spanning structure, distributes in membranes outside the nucleus and, within the nucleus, in membrane-less, liquid-like PML body biomolecular condensates. Detection of MALL in one or other environment was strictly dependent on the method of cell fixation used, suggesting that MALL adopts different conformations depending on its physical environment —lipidic or aqueous— in the cell. The acquisition of the condensate-compatible conformation requires PML expression. Excess MALL perturbed the distribution of the inner nuclear membrane proteins emerin and LAP2β, and that of the DNA-binding protein BAF, leading to the formation of aberrant nuclei. This effect, which is consistent with studies identifying overexpressed MALL as an unfavorable prognostic factor in cancer, could contribute to cell malignancy. Our study establishes a link between proteolipids, membranes and biomolecular condensates, with potential biomedical implications.

Plasmolipin and Its Role in Cell Processes

The mechanisms involved in the origin and development of malignant and neurodegenerative diseases are an important area of modern biomedicine. A crucial task is to identify new molecular markers that are associated with rearrangements of intracellular signaling and can be used for prognosis and the development of effective treatment approaches. The proteolipid plasmolipin (PLLP) is a possible marker. PLLP is a main component of the myelin sheath and plays an important role in the development and normal function of the nervous system. PLLP is involved in intracellular transport, lipid raft formation, and Notch signaling. PLLP is presumably involved in various disorders, such as cancer, schizophrenia, Alzheimer's disease, and type 2 diabetes mellitus. PLLP and its homologs were identified as possible virus entry receptors. The review summarizes the data on the PLLP structure, normal functions, and role in diseases.

A new insight to biomarkers related to resistance in survived-white spot syndrome virus challenged giant tiger shrimp, Penaeus monodon

The emergence of diseases such as white spot disease has become a threat to Penaeus monodon cultivation. Although there have been a few studies utilizing RNA-Seq, the cellular processes of host-virus interaction in this species remain mostly anonymous. In the present study, P. monodon was challenged with WSSV by intramuscular injection and survived for 12 days. The effect of the host gene expression by WSSV infection in the haemocytes, hepatopancreas and muscle of P. monodon was studied using Illumina HiSeq 2000. The RNA-Seq of cDNA libraries was developed from surviving WSSV-challenged shrimp as well as from normal healthy shrimp as control. A comparison of the transcriptome data of the two groups showed 2,644 host genes to be significantly up-regulated and 2,194 genes significantly down-regulated as a result of the infection with WSSV. Among the differentially expressed genes, our study discovered HMGB, TNFSF and c-Jun in P. monodon as new potential candidate genes for further investigation for the development of potential disease resistance markers. Our study also provided significant data on the differential expression of genes in the survived WSSV infected P. monodon that will help to improve understanding of host-virus interactions in this species.

Plasmolipin, PmPLP1, from Penaeus monodon is a potential receptor for yellow head virus infection

Plasmolipin has been characterized as a cell entry receptor for mouse endogenous retrovirus. In black tiger shrimp, two isoforms of plasmolipin genes, PmPLP1 and PmPLP2, have been identified from the Penaeus monodon EST database. The PmPLP1 is highly up-regulated in yellow head virus (YHV)-infected shrimp. Herein, the function of PmPLP1 is shown to be involved in YHV infection. The immunoblotting and immunolocalization showed that the PmPLP1 protein was highly expressed and located at the plasma membrane of gills from YHV-infected shrimp. Moreover, the PmPLP1 expressed in the Sf9 insect cells resided at the cell membrane rendering the cells more susceptible to YHV infection. Using the ELISA binding and mortality assays, the synthetic external loop of PmPLP1 was shown to bind the purified YHV and neutralize the virus resulting in the decrease in YHV infection. Our results suggested that the PmPLP1 was likely a receptor of YHV in shrimp.

Autoimmune T-cell reactivity to myelin proteolipids and glycolipids in multiple sclerosis

Central nervous system (CNS) myelin, the likely major target of autoimmune attack in multiple sclerosis (MS), contains a number of unique components that are potential targets of the attack. Two classes of molecules that are greatly enriched in CNS myelin compared to other parts of the body are certain types of proteolipids and glycolipids. Due to the hydrophobic nature of both of these classes of molecules, they present challenges for use in immunological assays and have therefore been somewhat neglected in studies of T-cell reactivity in MS compared to more soluble molecules such as the myelin basic proteins and the extracellular domain of myelin oligodendrocyte glycoprotein. This review firstly looks at the makeup of CNS myelin, with an emphasis on proteolipids and glycolipids. Next, a retrospective of what is known of T-cell reactivity directed against proteolipids and glycolipids in patients with MS is presented, and the implications of the findings are discussed. Finally, this review considers the question of what would be required to prove a definite role for autoreactivity against proteolipids and glycolipids in the pathogenesis of MS.

Two plasmolipins from the black tiger shrimp, Penaeus monodon and their response to virus pathogens

Two isoforms of plasmolipin were initially identified from the black tiger shrimp (Penaeus monodon) EST database and completed using 50 RACE to reveal complete cDNAs of 558 bp (PmPLP1) and 537 bp(PmPLP2) with 87% nucleotide sequence identity. The deduced amino acid sequences contained four-transmembrane domains and showed the highest amino acid identity (49% and 51%, respectively) to the honey bee (Apis mellifera) chemokine-like factor (CKLF), with a very similar hydrophobic pattern to other plasmolipins. Transcripts of PmPLP1 and PmPLP2 were observed in all tested shrimp tissues with the highest expression levels in the gill and epipodite for PmPLP1 and in the hemocytes and antennal gland for PmPLP2. PmPLP1 transcript levels were significantly upregulated in hemocytes at 24 and 72 h post infection (hpi) with yellow head virus (YHV) (7.4- and 14.7- fold, respectively), but only after 72 hpi by white spot syndrome virus (WSSV). In contrast, PmPLP2 was only slightly (but statistically significant)up-regulated with YHV and WSSV. Thus, PmPLPs have the potential to be a part of viral infection mechanisms or defense response. This is the first characterization of a plasmolipin gene in crustaceans.

The axo-myelinic synapse

Axons have evolved to acquire myelination, enabling denser packing and speedier transmission. Although myelin is considered a passive insulator, recent reports suggest a more dynamic role. Axons, in turn, are endowed with neurotransmitter release and uptake systems along their trunks. Based on these observations, I argue that there may exist a new type of chemical synapse between axon and myelin, one that supports activity-dependent communication between the two. This raises intriguing possibilities of dynamic fine-tuning of the myelin sheath even in adulthood, efficient recruitment of resources for myelin maintenance and bi-directional signaling, whereby the axon informs its myelinating cell of its metabolic needs proportionally to the electrical traffic it is transmitting. This would also have implications for de- and dysmyelinating diseases should this axo-myelinic synapse become dysfunctional.

Identification of the myelin protein plasmolipin as the cell entry receptor for Mus caroli endogenous retrovirus

The Asian wild mouse species Mus caroli harbors an endogenous retrovirus (McERV) that is closely related to but distinct from the endogenous retrovirus family defined by the Mus dunni endogenous virus and the Mus musculus endogenous retrovirus. McERV could infect some cell types from humans, dogs, and rats, but not all, and did not infect any mouse cell line tested. Because of its interesting host range and proposed ancestral relationship to primate retroviruses and because none of the entry receptors for this family of retroviruses had been identified, we began a search for the McERV receptor. We determined the chromosomal location of the receptor gene in the human genome by phenotypic screening of the G3 human-hamster radiation hybrid cell line panel and confirmed the localization by assaying for receptor activity conferred by bacterial artificial chromosome (BAC) clones spanning the region. We next localized the gene more precisely in one positive BAC by assaying for receptor activity following BAC digestion with several restriction enzymes that cleaved different sets of genes, and we confirmed that the final candidate gene, plasmolipin (PLLP; TM4SF11), is the novel receptor by showing that the expression of the human PLLP cDNA renders hamster and mouse cells susceptible to McERV infection. PLLP functions as a voltage-dependent potassium ion channel and is expressed primarily in kidney and brain, helping to explain the limited range of cell types that McERV can infect. Interestingly, mouse PLLP also functioned well as a receptor for McERV but was simply not expressed in the mouse cell types that we originally tested.

Myelin tetraspan family proteins but no non-tetraspan family proteins are present in the ascidian (Ciona intestinalis) genome

Several of the proteins used to form and maintain myelin sheaths in the central nervous system (CNS) and the peripheral nervous system (PNS) are shared among different vertebrate classes. These proteins include one-to-several alternatively spliced myelin basic protein (MBP) isoforms in all sheaths, proteolipid protein (PLP) and DM20 (except in amphibians) in tetrapod CNS sheaths, and one or two protein zero (P0) isoforms in fish CNS and in all vertebrate PNS sheaths. Several other proteins, including 2', 3'-cyclic nucleotide 3'-phosphodiesterase (CNP), myelin and lymphocyte protein (MAL), plasmolipin, and peripheral myelin protein 22 (PMP22; prominent in PNS myelin), are localized to myelin and myelin-associated membranes, though class distributions are less well studied. Databases with known and identified sequences of these proteins from cartilaginous and teleost fishes, amphibians, reptiles, birds, and mammals were prepared and used to search for potential homologs in the basal vertebrate, Ciona intestinalis. Homologs of lipophilin proteins, MAL/plasmolipin, and PMP22 were identified in the Ciona genome. In contrast, no MBP, P0, or CNP homologs were found. These studies provide a framework for understanding how myelin proteins were recruited during evolution and how structural adaptations enabled them to play key roles in myelination.

PLP2/A4 interacts with CCR1 and stimulates migration of CCR1-expressing HOS cells

Multiple CC chemokines bind to CCR1, which plays important roles in immune and inflammatory responses. To search for proteins involved in the CCR1 signaling pathway, we screened a yeast two-hybrid library using the cytoplasmic tail of CCR1 as the bait. One of the positive clones contained an open reading frame of 456bp, of which the nucleotide sequence was identical to that of proteolipid protein 2 (PLP2), also known as protein A4. Mammalian two-hybrid and coimmunoprecipitation analyses demonstrated the association of PLP2/A4 with CCR1. Indirect immunofluorescence analysis revealed that PLP2/A4 was predominantly located in plasma membrane and colocalized with CCR1 in transfected human HEK293 cells. In addition, focal staining of CCR1 appeared on the periphery of the membrane upon short exposure to Leukotactin-1(Lkn-1)/CCL15, a CCR1 agonist, and was costained with PLP2/A4 on the focal regions. PLP2/A4 mRNAs were detected in various cells such as U-937, HL-60, HEK293, and HOS cells. Overexpression of PLP2/A4 stimulated a twofold increase in the agonist-induced migration of HOS/CCR1 cells, implicating a functional role for PLP2/A4 in the chemotactic processes via CCR1.

Microarray analysis of postmortem temporal cortex from patients with schizophrenia

To examine molecular mechanisms associated with schizophrenia this study measured expression of approximately 12,000 genes in the middle temporal gyrus from 12 subjects with schizophrenia and 14 matched normal controls. Among the most consistent changes in genes with robust expression were significant decreases in the expression of myelination-related genes MAG, PLLP (TM4SF11), PLP1, ERBB3 in subjects with schizophrenia. There was also altered expression of genes regulating neurodevelopment (TRAF4, Neurod1, histone deacetylase 3), a circadian pacemaker (PER1), and several other genes involved in regulation of chromatin function and signaling mechanisms. These findings support the hypothesis that schizophrenia is associated with abnormalities in oligodendroglia and provide initial evidence suggesting a role for epigenetic mechanisms and altered circadian rhythms in this disorder.

Proteolipid plasmolipin: localization in polarized cells, regulated expression and lipid raft association in CNS and PNS myelin

The proteolipid plasmolipin is member of the expanding group of tetraspan (4TM) myelin proteins. Initially, plasmolipin was isolated from kidney plasma membranes, but subsequent northern blot analysis revealed highest expression in the nervous system. To gain more insight into the functional roles of plasmolipin, we have generated a plasmolipin-specific polyclonal antibody. Immunohistochemical staining confirms our previous observation of glial plasmolipin expression and proves plasmolipin localization in the compact myelin of rat peripheral nerve and myelinated tracts of the CNS. Western blot analysis indicates a strong temporal correlation of plasmolipin expression and (re-) myelination in the PNS and CNS. However, following axotomy plasmolipin expression is also recovered in non-regenerating distal nerve stumps. In addition, we detected plasmolipin expression in distinct neuronal subpopulations of the CNS. The observed asymmetric distribution of plasmolipin in compact myelin, as well as in epithelial cells of kidney and stomach, indicates a polarized cellular localization. Therefore, we purified myelin from the CNS and PNS and demonstrated an enrichement of phosphorylated plasmolipin protein in detergent-insoluble lipid raft fractions, suggesting selective targeting of plasmolipin to the myelin membranes. The present data indicate that the proteolipid plasmolipin is a structural component of apical membranes of polarized cells and provides the basis for further functional analysis.

Mass-spectrometric analysis of myelin proteolipids reveals new features of this family of palmitoylated membrane proteins

In this study, we have investigated the structure of the native myelin proteolipid protein (PLP), DM-20 protein and several low molecular mass proteolipids by mass spectrometry. The various proteolipid species were isolated from bovine spinal cord by size-exclusion and ion-exchange chromatography in organic solvents. Matrix-assisted laser desorption ionization-time of flight-mass spectrometry (MALDI-TOF-MS) of PLP and DM-20 revealed molecular masses of 31.6 and 27.2 kDa, respectively, which is consistent with the presence of six and four molecules of thioester-bound fatty acids. Electrospray ionization-MS analysis of the deacylated proteins in organic solvents produced the predicted molecular masses of the apoproteins (29.9 and 26.1 kDa), demonstrating that palmitoylation is the major post-translational modification of PLP, and that the majority of PLP and DM-20 molecules in the CNS are fully acylated. A series of myelin-associated, palmitoylated proteolipids with molecular masses raging between 12 kDa and 18 kDa were also isolated and subjected to amino acid analysis, fatty acid analysis, N- and C-terminal sequencing, tryptic digestion and peptide mapping by MALDI-TOF-MS. The results clearly showed that these polypeptides correspond to the N-terminal region (residues 1-105/112) and C-terminal region (residues 113/131-276) of the major PLP, and they appear to be produced by natural proteolytic cleavage within the 60 amino acid-long cytoplasmic domain. These proteolipids are not postmortem artifacts of PLP and DM-20, and are differentially distributed across the CNS.

Identification of MAL2, a novel member of the mal proteolipid family, though interactions with TPD52-like proteins in the yeast two-hybrid system

The TPD52 (tumor protein D52)-like proteins are small coiled-coil motif-bearing proteins which were first identified though their expression in human breast carcinoma. TPD52-like proteins are known to interact in hetero-and homomeric fashions, but there are no known heterologous binding partners for these proteins. We now report the cloning of a novel member of the MAL proteolipid family, named MAL2, though its interaction with a TPD52L2 bait in a yeast two-hybrid screen. MAL2 is predicted to be 176 residues (19 kDa) with four transmembrane domains and is 35.8% identical to MAL, a proteolipid required in apical vesicle transport. The MAL2 prey bound all TPD52-like baits tested in the yeast two-hybrid system and in vitro translation of MAL2 produced a single 19-kDa (35)S-labeled protein which specifically bound full-length GST-Tpd52 in GST pull-down assays. The gene MAL2, which was localized to human chromosomal band 8q23 and shown to consist of four exons, is predominantly expressed in human kidney, lung, and liver. Our study has therefore identified a novel member of the MAL proteolipid family and potentially implicates TPD52-like proteins in vesicle transport.

MAL, a proteolipid in glycosphingolipid enriched domains: functional implications in myelin and beyond

The myelin and lymphocyte protein MAL (VIP17/MVP17) is a proteolipid of 17 kD with a hydrophobicity pattern that indicates a four transmembrane domain structure. The MAL cDNA has been cloned from human T-cells, rat oligodendrocytes and the Madin-Darby canine kidney (MDCK) cell line. In the nervous system both myelinating cells, oligodendrocytes and Schwann cells, express MAL protein. MAL expression parallels myelin formation, and MAL is predominantly localized in compact myelin. Prior to myelin formation MAL is also found in immature Schwann cells. Outside the nervous system MAL expression is found in T-cells and in distinct epithelial cells, e.g. in kidney, stomach and thyroid gland, where MAL is localised in the apical plasma membrane. Specific glycosphingolipids, e.g. galactosylceramide and sulfatide, are enriched in such apical kidney and stomach membranes as well as in myelin. MAL copurifies with these glycosphingolipids in detergent insoluble domains, indicating a close association and possible functional interactions of MAL with glycosphingolipids in these tissues. Moreover, recent reports point to additional functions of MAL-glycosphingolipid complexes in signalling, cell differentiation and apical sorting. The role of MAL in the formation, stabilisation and maintenance of glycosphingolipid-enriched membrane microdomains and its contribution to specific membrane properties in myelin and epithelial cells are discussed.

VIP17/MAL, a lipid raft-associated protein, is involved in apical transport in MDCK cells

Apical proteins are sorted and delivered from the trans-Golgi network to the plasma membrane by a mechanism involving sphingolipid-cholesterol rafts. In this paper, we report the effects of changing the levels of VIP17/MAL, a tetraspan membrane protein localized to post-Golgi transport containers and the apical cell surface in MDCK cells. Overexpression of VIP17/MAL disturbed the morphology of the MDCK cell layers by increasing apical delivery and seemingly expanding the apical cell surface domains. On the other hand, expression of antisense RNA directed against VIP17/MAL caused accumulation in the Golgi and/or impaired apical transport of different apical protein markers, i.e., influenza virus hemagglutinin, the secretory protein clusterin (gp80), the transmembrane protein gp114, and a glycosylphosphatidylinositol-anchored protein. However, antisense RNA expression did not affect the distribution of E-cadherin to the basolateral surface. Because VIP17/MAL associates with sphingolipid-cholesterol rafts, these data provide functional evidence that this protein is involved in apical transport and might be a component of the machinery clustering lipid rafts with apical cargo to form apical transport carriers.

Structural and biochemical similarities reveal a family of proteins related to the MAL proteolipid, a component of detergent-insoluble membrane microdomains

The MAL gene encodes a proteolipid protein displaying a cell type-specific pattern of expression, including T lymphocytes, myelin-forming cells, and epithelial renal MDCK cells, which has been recently identified as a component of detergent-insoluble membranes known to be enriched in glycolipids and cholesterol. Sequence alignment revealed a high degree of conservation of the MAL protein across species and evidenced the existence of a significant level of overall identity between MAL and two other proteins, BENE and the plasmolipin proteolipid. Moreover, using subcellular fractionation of transiently transfected COS-7 cells, both MAL and BENE were identified in detergent-resistant membranes. These results suggest the existence of a novel family of MAL-related proteins (including MAL, BENE, and plasmolipin) with primary structure homologies and with the distinctive features of having unusual biochemical properties such as lipid-like behaviour and/or the ability to reside in glycolipid-enriched membrane microdomains.

Colonic epithelium-enriched protein A4 is a proteolipid that exhibits ion channel characteristics

Expression of the human gene A4 is enriched in the colonic epithelium and is transcriptionally activated on differentiation of colonic epithelial cells in vitro (M. M. Oliva, T. C. Wu, and V. W. Yang. Arch. Biochem. Biophys. 302: 183-192, 1993). A4 cDNA contains an open reading frame that predicts a polypeptide of 17 kDa. To determine the function of the A4 protein, we characterized its biochemical and physiological properties. Hydropathy analysis of deduced A4 amino acid sequence revealed four putative membrane-spanning alpha-helices. The hydrophobic nature of A4 was confirmed by its being extractable with organic solvents. Immunocytochemical studies of cells expressing A4 localized it to the endoplasmic reticulum. Moreover, A4 multimerized in vivo as determined by coimmunoprecipitation experiments. The four-transmembrane topology and biophysical characteristics of A4 suggest that it belongs to a family of integral membrane proteins called proteolipids, some of which multimerize to form ion channels. Subsequent electrophysiological studies of nuclei isolated from microinjected Xenopus laevis oocytes transiently expressing A4 showed the appearance of a 28-pS channel. Thus our studies indicate that A4 is a colonic epithelium-enriched protein localized to the endoplasmic reticulum and that, similar to other proteolipids, A4 multimerizes and exhibits characteristics of an ion channel.

Full-lenth cloning, expression and cellular localization of rat plasmolipin mRNA, a proteolipid of PNS and CNS

We have isolated a 1.476 bp cDNA (NTII11) representing a transcript that is differntially expressed during sciatic nerve development and regeneration in the rat. Nucleotide sequence comparison indicates partial identity with a recently isolated plasmolipin cDNA. However, our clone extends the published sequence by 234 bp at the 5' end and predicts a protein that contains an additional 25 amino acids at th N-terminus. The open reading frame of th NTII11 transcript encodes a 19.4 kDa protein with four putative transmembrane domains. Northern blot analyses revealed a tissue-specific expression was confirmed by in situ hybridization, and cellular localization of plasmolipin mRNA was demonstrated in Schwann cells of the sciatic nerve and in glial cells of myelinated brain structures. The steady-state levels of plasmolipin mRNA were markedly altered (i) during development of sciatic nerve and brain. (ii) after sciatic nerve injury, and (ii) in cured Schwann cells maintained under different conditions of cell growth and arrest. Our data indicate a function of plasmolipin during myelination in the central as well as in the peripheral nervous system.

Schwann cell development, differentiation and myelination

Neu-differentiation factor (glial growth factor) has been established as an important regulator of early Schwann cell development, and the lineage relationship between immature Schwann cells and the neural crest has been clarified by the identification of the Schwann cell precursor. Progress has been made in identifying transcription factors that control Schwann cell development and in defining molecules that positively and negatively regulate myelin differentiation pathways. The tetraspan group has emerged as a set of proteins with prominent functions in Schwann cell biology.

Cloning and characterization of MVP17: a developmentally regulated myelin protein in oligodendrocytes

The remarkable quantities of myelin membrane produced by oligodendrocytes has led us to examine the mechanisms involved in the sorting and transport of proteins and lipids during myelinogenesis. Noting that it has been proposed that proteins destined for the apical surface of polarized epithelial cells co-cluster with glycolipid-rich microdomains during sorting and transport from the trans-Golgi network (Simons and van Meer: Biochemistry 27:6197-6202, 1988; Simons and Wandinger-Ness: Cell 62:207-210, 1990), we hypothesized that the glycolipid-rich oligodendrocytes may adopt this mechanism for myelinogenesis. Protein-lipid complexes from oligodendrocytes and myelin were isolated utilizing detergent insolubility and two-dimensional gel electrophoresis. A developmentally regulated protein, MVP17 (myelin vesicular protein of 17 kDa), was identified. Microsequencing of the N-terminal peptide revealed a high homology to human T-cell MAL protein (Alonso and Weissman: Proc Natl Acad Sci USA 84:1997-2001, 1987). The corresponding MVP17 cDNA was isolated from an oligodendrocyte cDNA library. The predicted protein sequence showed 88.9% identity with MAL, and the hydrophobicity profile suggested four transmembrane domains. In vitro translation demonstrated a signal at the deduced Mr of approximately 17 kDa. Northern analyses indicated that MVP17 mRNA expression is restricted to brain and kidney and that this expression is up-regulated in oligodendrocytes and brain during the period of active myelination. These data suggest that MVP17 is involved in myelin biogenesis and/or myelin function.

Expression of myelin proteolipid protein in oligodendrocytes and transfected cells

The data presented in this paper show that the appropriate tools are now available to study the behavior of PLP and DM20 transcripts engineered with either point mutations or deletion of specific domains. Such studies should begin to provide new insights into the functions of PLP and DM20 and their role in relation to the optimal functioning of the nervous system.