Characterization of three saccharomyces cerevisiae (SJNL) genes that have homology to a family of phosphatidylinositol phosphatase genes / Sudha Srinivasan.

Format:

Book

Manuscript

Microformat

Thesis/Dissertation

Author/Creator:

Srinivasan, Sudha.

Contributor:

Nussbaum, Robert L., 1950- advisor.

University of Pennsylvania.

Language:

English

Subjects (All):

Penn dissertations--Molecular biology.

Molecular biology--Penn dissertations.

Molecular Biology.

Academic Dissertations as Topic.

Medical Subjects:

Molecular Biology.

Academic Dissertations as Topic.

Local Subjects:

Penn dissertations--Molecular biology.

Molecular biology--Penn dissertations.

Physical Description:

xv, 194 pages : illustrations ; 29 cm

Production:

1996.

Summary:

Sequence analysis of the genome database of the budding yeast, Saccharomyces cerevisiae has uncovered three putative phosphatidylinositol phosphatases (Ptdlns) SJNL1, SJNL2 and SJNL3 for Synaptojanin-Like (GenBank ID #s - P40559, Z50161 and P42837 respectively) that share the highly conserved inositol phosphatase domains present in a family of phosphatidylinositol phosphatases. This family includes the recently characterized Synaptojanin, and the product of the gene defective in the Oculocerebrorenal (OCRL) syndrome of Lowe. In addition, the SJNL gene products possess as does Synaptojanin regions of homology to the yeast Sac1p protein which has been genetically implicated in inositol metabolism and in the function of the actin cytoskeleton. Synaptojanin has been proposed to have a role in endocytosis and synaptic vesicular trafficking.

Extensive studies in yeast indicates that phosphoinositide synthesis and turnover is linked to a variety of membrane trafficking events. In order to understand the physiological function of the three SJNL gene products, we sequentially performed gene disruptions of each gene. We then executed a series of phenotypic characterizations on the various mutant strains to determine if (1) the three SJNL gene products were enzymes in the phosphatidylinositol signaling pathway and (2) they played a role in protein and/or membrane trafficking. Gene disruptions of the three SJNL genes revealed that the Sjnl proteins were not essential for life. Protein sorting assays demonstrate that the different genes when disrupted do not cause a defect in vacuolar protein sorting functions. The mutant SJNL strains do however exhibit striking defects in vacuolar morphology and distinctive patterns of osmosensitivities. They also possess an unusual cold insensitivity phenotype that enables them to grow at nonpermissive temperatures (below 15$\sp\circ$C). Vacuole labeling and electron microscopy studies implicate at least one or two of the SJNL proteins as having a role in endocytosis. We postulate that while these gene products belong to the same family, they are not redundant in function and have distinct roles in maintaining the integrity of the vacuole, perhaps the biogenesis/assembly of the vacuole. In addition, they also appear to have a function in endocytosis from the plasma membrane and perhaps in regulating membrane composition.

Notes:

Supervisor: Robert L. Nussbaum.

Thesis (Ph.D. in Molecular Biology) -- University of Pennsylvania, 1996.

Includes bibliographical references.

Local Notes:

University Microfilms order no.: 97-13008.

OCLC:

187469459