Gene/Protein Disease Symptom Drug Enzyme Compound
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 4,927 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In epithelial cells the plasma membrane is divided into domains that are biochemically and functionally different. In intestinal cells for example the apical domain is facing the intestinal lumen and is involved in the uptake of nutriments while the basolateral domain is mediating cell-cell adhesion and signalisation. We are interested in deciphering the mechanisms underlying the creation and maintenance of such specialized domains. As an epithelial model we have used the intestinal cell line Caco-2 and we have studied the transport and sorting of the human neurotrophin receptor (p75 NTR) in these cells. Newly synthesized p75 NTR is first transported to the basolateral membrane and then is accumulated on the apical membrane after transcytosis. This final apical localization is controlled by the presence of a membrane anchor and a cluster of O-glycosylation sites located in the part of the ectodomain close to the membrane. Among the mechanisms likely to be involved in the sorting of apical components we have looked for a role of lipid-protein microdomain formation in the Golgi apparatus. These membrane microdomains are highly enriched in glycosylphosphatidyl inositol (GPI) anchored proteins, glycosphingolipids and apical proteins such as sucrase isomaltase (SI). Such a composition is also found for endocytic structures called caveolae which are made of caveolin 1. We have expressed caveolin 1 in Caco-2 cells which do not express it and also caveolin 2, a related protein of unknown function. Expression of caveolin 1 led to formation of caveolae indicating that this protein is necessary for caveolae formation while caveolin 2 is restricted to the Golgi apparatus and has no effect on caveolae formation. However Caveolin 2 increased the amount of SI incorporated in microdomains suggesting a role in recruitment into the apical pathway. The choice for a site of fusion for transport vesicles is the last step of control during exocytosis. To identify proteins involved in that step we have cloned and characterized two members of the t-SNARE family, namely syntaxin 3 and SNAP23. Syntaxin 3 is present on the apical membrane and forms a complex with SNAP23 which is also localized on the basolateral membrane where it forms a complex with syntaxin 4. Overexpression of syntaxin 3 in Caco-2 led to a decrease of SI exocytosis towards the apical membrane confirming that syntaxin 3 is involved in targeting the fusion of apical transport vesicles to the apical pole of the cells.
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PMID:[Identification of signals and mechanisms of sorting of plasma membrane proteins in intestinal epithelial cells]. 1045 45

Polarized traffic in epithelial cells depends on well-organized pathways that direct secretory cargo to the apical or basolateral plasma membrane. In MDCK cells, apical trafficking can be further divided into a lipid raft-dependent and a raft-independent route, which separate biosynthetic cargo in a post-Golgi endosomal compartment. We have now identified KIF5C as a kinesin motor for apical trafficking of both raft-associated sucrase isomaltase and raft-independent neurotrophin receptor. KIF5C was identified by mass spectrometry in vesicle enriched fractions and on immunoisolated post-Golgi vesicles carrying apical cargo. The amount of vesicle-associated KIF5C was highest on material isolated directly after trans-Golgi network release and declined thereafter. Altogether, our data suggest that KIF5C is involved in the passage of apical cargo molecules to a post-Golgi endosomal compartment, where further segregation into distinct vesicle populations proceeds.
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PMID:KIF5C, a kinesin motor involved in apical trafficking of MDCK cells. 2009 56