PMID: 10921916

 

    Legend: Sugar

Title : Specific isoforms of the resident endoplasmic reticulum protein glucosidase II associate with the CD45 protein- tyrosine phosphatase via a lectin-like interaction

Abstract :

1. We have previously demonstrated that CD45 physically associates with the endoplasmic reticulum processing enzyme glucosidase II ( GII )
2. GII consists of the catalytic alpha-chain chain and an associated beta- chain
3. To gain insight into the basis of the association between CD45 and GII , we examined the biochemical requirements for the interaction
4. We show that the alpha- subunit is essential for the interaction
5. Interestingly, only a higher molecular weight form of GIIalpha is capable of associating with CD45 in a competitive situation where multiple GIIalpha isoforms are expressed
6. Further, transfection studies demonstrate that only isoforms containing the alternatively spliced sequence Box A1 are capable of binding CD45 , although all isoforms are catalytically active
7. The interaction between CD45 and GII is dependent on the active site of GII , is mediated through the carbohydrate on CD45 , and can be inhibited with mannose.
8. Taken together, these results suggest that GIIalpha acts as a lectin and binds to CD45 in an exon-dependent manner
9. This lectin activity of GII may be a novel mechanism for the regulation of CD45 biology and play a role in immune function, possibly by regulating CD45 glycosylation