The secreted form of a melanocyte membrane-bound glycoprotein (Pmel17/gp100) is released by ectodomain shedding

FASEB J. 2010 Mar;24(3):916-30. doi: 10.1096/fj.09-140921. Epub 2009 Nov 2.


Ectodomain shedding is a proteolytic mechanism by which a transmembrane protein is converted into a secreted form. Pmel17/gp100 is a melanocyte-specific membrane-bound glycoprotein that has amyloid characteristics and forms fibrillar structures in melanosomes after a complex sequence of post-translational processing and trafficking events, including cleavage by a furin-like proprotein convertase (PC). A secreted form of Pmel17 (termed sPmel17) was also thought to be released due to cleavage by a PC. We used multidisciplinary approaches to demonstrate that sPmel17 is released by ectodomain shedding at the juxtamembrane and/or intramembrane motif and to show that this is independent of cleavage by a PC. We further show that sPmel17 consists of 2 fragments linked by disulfide bonds and that the shedding is inhibited at low temperature but not by metalloproteinase inhibitors. Moreover, treatment with a phorbol ester or a calmodulin inhibitor induces Pmel17 shedding. We also refine the reactivity of HMB50 and NKI/beteb, 2 monoclonal antibodies commonly used as melanoma-specific markers. The fact that those antibodies require physically separated domains of Pmel17 sheds interesting light on its 3-dimensional conformation. We conclude that sPmel17 is released by regulated proteolytic ectodomain shedding.-Hoashi, T., Tamaki, K., Hearing, V. J. The secreted form of a melanocyte membrane-bound glycoprotein (Pmel17/gp100) is released by ectodomain shedding.

Publication types

  • Research Support, N.I.H., Intramural

MeSH terms

  • Adenoviridae
  • Animals
  • Antibodies, Monoclonal / metabolism
  • Calmodulin / antagonists & inhibitors
  • Cell Line
  • Cell Line, Tumor
  • Glycosylation
  • HeLa Cells
  • Humans
  • Immunoblotting
  • Immunoprecipitation
  • Melanocytes / drug effects
  • Melanocytes / metabolism*
  • Membrane Glycoproteins / chemistry
  • Membrane Glycoproteins / genetics
  • Membrane Glycoproteins / metabolism*
  • Microscopy, Fluorescence
  • Phorbol Esters / pharmacology
  • Phosphorylcholine / analogs & derivatives
  • Phosphorylcholine / pharmacology
  • Polymethacrylic Acids / pharmacology
  • Proprotein Convertases / metabolism
  • Protein Binding / drug effects
  • Protein Structure, Tertiary / genetics
  • Protein Structure, Tertiary / physiology
  • Rabbits
  • Sodium Azide / pharmacology
  • Sulfonamides / pharmacology
  • gp100 Melanoma Antigen


  • Antibodies, Monoclonal
  • Calmodulin
  • Membrane Glycoproteins
  • PMEL protein, human
  • Phorbol Esters
  • Polymethacrylic Acids
  • Sulfonamides
  • gp100 Melanoma Antigen
  • poly(MPC-co-MA)
  • Phosphorylcholine
  • W 7
  • Sodium Azide
  • Proprotein Convertases