{'fraction_non_alphanumeric': 0.03194103194103194, 'fraction_numerical': 0.028255528255528257, 'mean_word_length': 5.464285714285714, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 1, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
The secreted form of a melanocyte membrane‐bound glycoprotein (Pmel17/gp100) is released by ectodomain shedding

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. FASEB J. 24, 916–930 (2010). www.fasebj.org