Degradation of alpha-melanocyte stimulating hormone (alpha-MSH) by CALLA/endopeptidase 24. 11 expressed by human melanoma cells in culture
✍ Scribed by Monique Deschodt-Lanckman; Yves Vanneste; Béatrice Loir; Alain Michel; Anita Libert; Ghanem Ghanem; Ferdinand Lejeune
- Book ID
- 102866437
- Publisher
- John Wiley and Sons
- Year
- 1990
- Tongue
- French
- Weight
- 654 KB
- Volume
- 46
- Category
- Article
- ISSN
- 0020-7136
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✦ Synopsis
The common acute lymphoblastic leukemia antigen (CALLA) is identical to human endopeptidase 24.1 I (E-24.1 I)
and is expressed on certain human melanoma lines. This work was conducted in order t o investigate whether alphamelanocyte-stimulating hormone (alpha-MSH) could be a substrate for E-24.1 I , its degradation leading t o the negative alpha-MSH radiobinding assay results observed with some CALLA-positive cell lines. We used 3 human melanoma cell lines (GLL-19, Me1 Juso and G361) which lack receptors to alpha-MSH and express CALLA, and, as a control, one CALLA-negative melanoma cell line (HBL) with specific receptors for alpha-MSH. Radioimmunoassays give evidence that alpha-MSH was degraded in the presence of the 4 melanoma cell lines and that disappearance of the peptide was significantly reduced by phosphoramidon in 2 lines (GLLIP and G361). Upon incubation of alpha-MSH with GLL-I9 and G361 cell membranes, 3 degradation products were completely abolished in the presence of phosphoramidon. Amino acid content analysis of alpha-MSH fragments produced by purified E-24. I I permitted identification of 6 peptide bonds in the sequence of alpha-MSH susceptible to cleavage by the enzyme. It is concluded that alpha-MSH is a substrate in vitro for purified E-24. I I and for the enzyme present on the human melanoma cell lines GLL-I9 and G361, expressing a high level of endopeptidase activity. However, hydrolysis of alpha-MSH by this enzyme does not seem t o represent the main factor responsible for the apparent absence of receptors for the hormone on some cell lines.