We investigated whether human lysosomal hydrolases, in common with secretory and plasma membrane glycoproteins, associate with the ER chaperone calnexin. Neither $ alpha$- or $ beta$-chains of $ beta$-hexosaminidase A, cathepsin D, nor the endogenous proteases cathepsins B or L associated with calnexin in COS-I cells. Hex $ alpha$-chains misfolded due to either the incorporation of azetidine-2-carboxylic acid, treatment with dithiothreitol, or the presence of a Tay-Sachs Disease mutation (leading to retention of Hex A $ alpha$-chains in the ER) also did not associate with calnexin. Chemical-crosslinking reagents or long-term labeling also failed to show a Hex A $ alpha$-chain association with calnexin. Lysosomal hydrolases also did not associate with the ER chaperone calreticulin. Surprisingly, $ alpha$-L-iduronidase and Hex A $ alpha$-chains associated with calnexin when overexpressed using a CMV promoter. The segregation of lysosomal hydrolases from secretory proteins thus occurs at an earlier stage than predicted. Hydrolase folding appears to be controlled by a pathway different from that used by secretory and plasma membrane glycoproteins.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.24047 |
| Date | January 1996 |
| Creators | Wilson, Daniel James, 1970. |
| Contributors | Hechtman, Peter (advisor), Kaplan, Feigie (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Master of Science (Department of Biology.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001537686, proquestno: MM19857, Theses scanned by UMI/ProQuest. |
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