Abstract
The synaptojanins represent a subfamily of inositol 5'-phosphatases that contain an NH2-terminal Sac1p homology domain. A nerve terminal-enriched synaptojanin, synaptojanin 1, was previously proposed to participate in the endocytosis of synaptic vesicles and actin function. The genome of Saccharomyces cerevisiae contains three synaptojanin-like genes (SJL1, SJL2 and SJL3), none of which is essential for growth. We report here that a yeast mutant lacking SJL1 and SJL2 (Deltasjl1 Deltasjl2) exhibits a severe defect in receptor-mediated and fluid-phase endocytosis. A less severe endocytic defect is present in a Deltasjl2 Deltasjl3 mutant, while endocytosis is normal in a Deltasjl1 Deltasjl3 mutant. None of the mutants are impaired in invertase secretion. The severity of the endocytic impairment of the sjl double mutants correlates with the severity of actin and polarity defects. Furthermore, the deletion of SJL1 suppresses the temperature-sensitive growth defect of sac6, a mutant in yeast fimbrin, supporting a role for synaptojanin family members in actin function. These findings provide a first direct evidence for a role of synaptojanin family members in endocytosis and provide further evidence for a close link between endocytosis and actin function.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, Non-P.H.S.
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Actins / analysis
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Actins / metabolism
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Biological Transport / physiology
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Cell Polarity / physiology
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Clathrin / analysis
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Clathrin / genetics
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Clathrin / metabolism
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Dynamins
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Endocytosis / physiology*
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Enzyme Inhibitors / metabolism*
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Fungal Proteins / analysis
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Fungal Proteins / genetics
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Fungal Proteins / metabolism
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GTP Phosphohydrolases / analysis
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GTP Phosphohydrolases / genetics
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GTP Phosphohydrolases / metabolism
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Gene Expression Regulation, Enzymologic
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Gene Expression Regulation, Fungal
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Glycoside Hydrolases / metabolism
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Microscopy, Electron
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Mitochondria / chemistry
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Mitochondria / enzymology
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Mitochondria / ultrastructure
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Mutagenesis / physiology
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Nerve Tissue Proteins / analysis*
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Nerve Tissue Proteins / genetics
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Nerve Tissue Proteins / metabolism*
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Phosphoric Monoester Hydrolases / analysis*
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Phosphoric Monoester Hydrolases / genetics
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Phosphoric Monoester Hydrolases / metabolism*
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Saccharomyces cerevisiae / chemistry*
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Saccharomyces cerevisiae / enzymology
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Saccharomyces cerevisiae / genetics
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Vacuoles / chemistry
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Vacuoles / enzymology
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Vacuoles / ultrastructure
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beta-Fructofuranosidase
Substances
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Actins
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Clathrin
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Enzyme Inhibitors
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Fungal Proteins
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Nerve Tissue Proteins
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synaptojanin
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Phosphoric Monoester Hydrolases
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myo-inositol-1 (or 4)-monophosphatase
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Glycoside Hydrolases
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beta-Fructofuranosidase
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GTP Phosphohydrolases
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Dynamins