Prosaposin is a multifunctional glycoprotein with different molecular masses and dual destinations. A 65 kDa form of prosaposin is targeted to lysosomes and converted by partial proteolysis, into four smaller non-enzymatic saposin A-D required for the hydrolysis of glycosphingolipids. However, the 65 kDa protein may be further glycosylated to a 70 kDa secretory form that is found in various biological fluids and suspected to have a trophic activity. Mutations of the prosaposin gene are linked to several lysosomal disorders. This thesis examines various aspects of the synthesis, targeting and function of prosaposin, and for practical purposes, the results and discussion were divided in three main sections. The first part deals with the cloning of the mouse prosaposin gene, the analysis of its transcribed mRNA and translation products. The second section examines the mechanism of targeting of the 65 kDa protein to lysosomes using mutagenic analyses. The third part deals with the effect of the inactivation of the prosaposin gene on the development of the male reproductive system. Sequence analysis revealed that the mouse prosaposin gene is over 20 kb in length and composed of 15 exons and 14 introns. Two forms of alternatively spliced mRNA (including or excluding exon 8) were found by RT-PCR in a tissue specific manner. Structure analysis and secondary structure predictions among mouse, rat and human prosaposins illustrated a common framework of amino acids forming amphiphatic helices enclosing an internal hydrophobic core implicated on their interaction with lipids. Mutagenic deletions of functional domains of prosaposin demonstrated that its C-terminus was required for the lysosomal targeting of this protein. Further evidence from chimeric constructs of albumin attached to various functional domains of prosaposin, suggested that the C-terminus plus at least one saposin domain are necessary for the targeting of albumin to lysosomes. Investigation of the effect of p
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.36857 |
| Date | January 2000 |
| Creators | Zhao, Qing, 1966- |
| Contributors | Morales, Carlos R. (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 | Doctor of Philosophy (Department of Anatomy and Cell Biology.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001771044, proquestno: NQ69952, Theses scanned by UMI/ProQuest. |
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