Targeting of MAL, a putative element of the apical sorting machinery, to glycolipid-enriched membranes requires a pre-golgi sorting event |
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Authors: | R Puertollano MA Alonso |
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Affiliation: | Centro de Biología Molecular "Severo Ochoa,", Universidad Autónoma de Madrid, Consejo Superior de Investigaciones Científicas, Madrid, Cantoblanco, 28049-, Spain. |
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Abstract: | The MAL proteolipid is a nonglycosylated polytopic membrane protein with specific residence in glycolipid-enriched membrane (GEM) microdomains. MAL has been proposed as an element of the machinery for apical transport in polarized epithelial cells. Previous work demonstrated that MAL requires its four carboxyl-terminal amino acids to be targeted to GEMs. In the present work, we have engineered MAL with N-glycosylation consensus sequences to delimit the site at which commitment of MAL to access into GEMs takes place. Comparison of engineered MAL proteins bearing either an intact or a truncated carboxyl terminus revealed that whereas the former acquired endo H-sensitive and endo H-resistant mature glycosylation, the protein with a deleted carboxyl terminus did not. These results indicate that although MAL incorporation into GEMs takes place mainly in the Golgi, commitment of MAL to enter GEMs is a pre-Golgi event. |
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