Melanocyte protein PMEL also known as premelanosome protein (PMEL), silver locus protein homolog (SILV) or Glycoprotein 100 (gp100), is a protein that in humans is encoded by the PMEL gene.[5][6] Its gene product may be referred to as PMEL, silver, ME20, gp100 or Pmel17.

PMEL
Available structures
PDBOrtholog search: PDBe RCSB
Identifiers
AliasesPMEL, D12S53E, ME20, ME20-M, ME20M, P1, P100, PMEL17, SI, SIL, SILV, gp100, premelanosome protein, HMB-45, HMB45
External IDsOMIM: 155550; MGI: 98301; HomoloGene: 5048; GeneCards: PMEL; OMA:PMEL - orthologs
Orthologs
SpeciesHumanMouse
Entrez
Ensembl
UniProt
RefSeq (mRNA)

NM_021882

RefSeq (protein)

NP_001186982
NP_001186983
NP_001307050
NP_001307051
NP_008859

NP_068682

Location (UCSC)Chr 12: 55.95 – 55.97 MbChr 10: 128.54 – 128.56 Mb
PubMed search[3][4]
Wikidata
View/Edit HumanView/Edit Mouse

Structure and function

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PMEL is a 100 kDa, 661 amino acids long type I transmembrane glycoprotein that is expressed primarily in melanosomes, which are the melanin-producing organelles in melanocytes of pigment cells of the skin and eye, and in most malignant melanomas.

This protein is involved in melanosome maturation, including melanogenesis, melanosome biogenesis, and melanin polymerization (Eisenberg) [1]. The transmembrane form of PMEL is modified in the secretory pathway by elaboration of N-linked oligosaccharides and addition and modification of O-linked oligosaccharides. It is then targeted to precursors of the pigment organelle, the melanosome, where it is proteolytically processed to several small fragments. Some of these fragments form non-pathological amyloid that assemble into sheets and form the striated pattern that underlies melanosomal ultrastructure. PMEL cleavage is mediated by several proteases including a proprotein convertase of the furin family, a "sheddase" that might include members of the a disintegrin and metalloproteinase (ADAM) family, and additional proteases in melanosomes or their precursors. After the amyloidogenic region is cleaved, the small remaining integral membrane fragment is digested by γ-secretase.

The expression of the PMEL gene is regulated by the microphthalmia-associated transcription factor (MITF).[7][8]

Function in cancer and cancer treatment

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The gp100 protein is a melanoma antigen i.e. a tumor-associated antigen.

Short fragments of it have been used to develop the gp100 cancer vaccine which is or contains gp100:209-217(210M).[9]

Hydrophilic recombinant gp100 protein (HR-gp100) has been topically applied on human intact skin in vitro, and used as a vaccine in a mouse model. It was demonstrated that HR-gp100 permeates into human skin, and is processed and presented by human dendritic cells. In the mouse model, an HR-gp100-based vaccine triggered antigen-specific T cell responses, as shown by proliferation assays, ELISA and intracellular staining for IFN-γ.

The gp100 protein contains differentiation antigens.[2], and has been widely studied to be used as a target for melanoma immunotherapy. Different sequences of the GP100 peptide could be used for immunization against tumors. According to a case study, modifications of GP100, such as GP100-209 and GP100-208, have shown a greater number of antigen-specific CTL's (cytotoxic T lymphocytes), which can target and kill cancer cells (Eisenberg).[3]

References

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  1. ^ a b c GRCh38: Ensembl release 89: ENSG00000185664Ensembl, May 2017
  2. ^ a b c GRCm38: Ensembl release 89: ENSMUSG00000025359Ensembl, May 2017
  3. ^ "Human PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
  4. ^ "Mouse PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
  5. ^ Kim KK, Youn BS, Heng HH, Shi XM, Tsui LC, Lee ZH, Pickard RT, Kwon BS (Oct 1996). "Genomic organization and FISH mapping of human Pmel 17, the putative silver locus". Pigment Cell Res. 9 (1): 42–8. doi:10.1111/j.1600-0749.1996.tb00085.x. PMID 8739560.
  6. ^ "Entrez Gene: SILV silver homolog (mouse)".
  7. ^ Du J, Miller AJ, Widlund HR, Horstmann MA, Ramaswamy S, Fisher DE (2003). "MLANA/MART1 and SILV/PMEL17/GP100 are transcriptionally regulated by MITF in melanocytes and melanoma". Am. J. Pathol. 163 (1): 333–43. doi:10.1016/S0002-9440(10)63657-7. PMC 1868174. PMID 12819038.
  8. ^ Hoek KS, Schlegel NC, Eichhoff OM, Widmer DS, Praetorius C, Einarsson SO, Valgeirsdottir S, Bergsteinsdottir K, Schepsky A, Dummer R, Steingrimsson E (2008). "Novel MITF targets identified using a two-step DNA microarray strategy". Pigment Cell Melanoma Res. 21 (6): 665–76. doi:10.1111/j.1755-148X.2008.00505.x. PMID 19067971. S2CID 24698373.
  9. ^ "NCI Drug Dictionary". National Cancer Institute.

Further reading

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  • Overview of all the structural information available in the PDB for UniProt: P40967 (Melanocyte protein PMEL) at the PDBe-KB.