Shedding and gamma-secretase-mediated intramembrane proteolysis of the mucin-type molecule CD43

• Published in: Biochemical journal 2005-04, Vol.387 (Pt 2), p.377-384
• Main Authors: Andersson, Christian X, Fernandez-Rodriguez, Julia, Laos, Sirle, Baeckström, Dan, Haass, Christian, Hansson, Gunnar C
• Format: Article
• Language: English
• Subjects: Amyloid Precursor Protein Secretases; Animals; Antigens, CD - genetics; Antigens, CD - metabolism; Aspartic Acid Endopeptidases - metabolism; Cell Line; Endopeptidases; Gene Expression; Humans; Leukosialin; Membrane Proteins - genetics; Membrane Proteins - metabolism; Mutagenesis, Site-Directed; Plasmids; Presenilin-1; Protein Processing, Post-Translational; Protein Structure, Tertiary; Recombinant Proteins; Sialoglycoproteins - genetics; Sialoglycoproteins - metabolism
• ISSN: 0264-6021; 1470-8728
• DOI: 10.1042/BJ20041387

CD43 is a transmembrane molecule that contains a 123-aminoacids-long cytoplasmic tail and a highly O-glycosylated extracellular domain of mucin type. Endogenous CD43 expressed in COLO 205, K562 and Jurkat cells revealed a membrane-associated, 20 kDa CD43-specific cytoplasmic tail fragment (CD43-CTF) upon inhibition of gamma-secretase. This fragment was formed by an extracellular cleavage, as it was not accumulated after treating cells with 1,10-phenanthroline, a metalloprotease inhibitor. When CD43 was transfected into HEK-293 cells expressing dominant-negative PS1 (presenilin-1), the CD43-CTF was accumulated, but not in cells with wild-type PS1. Owing to its accumulation in the presence of a non-functional PS variant, it may thus be a novel gamma-secretase substrate. This CTF is formed by an extracellular cleavage close to the membrane, is a fragment that can be concluded to be a substrate for gamma-secretase. However, the intracellular gamma-secretase product has not been possible to detect, suggesting a quick processing of this product. During normal growth the CTF was not found without gamma-secretase inhibition, but when the cells (COLO 205) were very confluent the fragment could be detected. The intracellular domain of CD43 has previously been shown to contain a functional nuclear localization signal, and has been suggested to be involved in gene activation. From this and the present results, a novel way to explain how mucin-type molecules may transduce intracellular signals can be proposed.