Lipid kinases and their phosphorylated products are important regulators of many cellular processes, including intracellular membrane traffic. The best example of this is provided by the class III phosphoinositide 3-kinase (PI-3K), Vps34p, which is required for correct targeting of newly synthesized carboxypeptidase Y to the yeast vacuole. A probable mammalian Vps34p orthologue has been previously identified, but its function in the trafficking of lysosomal enzymes has not been resolved. To investigate the possible role(s) of mammalian Vps34p in protein targeting to lysosomes, we have cloned the rat orthologue and overexpressed a kinase-deficient mutant in HeLa cells. Expression of the mutant protein inhibited both maturation of procathepsin D and basal secretion of the precursor. In contrast wortmannin, which also inhibited maturation, caused hypersecretion of the precursor. We propose that mammalian Vps34p plays a direct role in targeting lysosomal enzyme precursors to the endocytic pathway in an analogous fashion to its role in the fusion of early endocytic vesicles with endosomes. We further suggest that inhibition of a wortmannin-sensitive enzyme, other than mammalian Vps34p, is responsible for the failure to recycle unoccupied mannose 6-phosphate receptors to the trans-Golgi network, and consequent hypersecretion of lysosomal enzyme precursors observed in the presence of this drug.
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February 2001
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Research Article|
January 25 2001
Overexpression of a rat kinase-deficient phosphoinositide 3-kinase, Vps34p, inhibits cathepsin D maturation
Paula E. ROW;
Paula E. ROW
1
*Wellcome Trust Centre for the Study of Molecular Mechanisms in Disease, University of Cambridge, Addenbrookes Hospital, Hills Road, Cambridge CB2 2XY, U.K.
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Barbara J. REAVES;
*Wellcome Trust Centre for the Study of Molecular Mechanisms in Disease, University of Cambridge, Addenbrookes Hospital, Hills Road, Cambridge CB2 2XY, U.K.
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Jan DOMIN;
Jan DOMIN
3
†Ludwig Institute for Cancer Research, University College London School of Medicine, Riding House Street, London W1P 8BT, U.K.
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J. Paul LUZIO;
J. Paul LUZIO
*Wellcome Trust Centre for the Study of Molecular Mechanisms in Disease, University of Cambridge, Addenbrookes Hospital, Hills Road, Cambridge CB2 2XY, U.K.
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Howard W. DAVIDSON
Howard W. DAVIDSON
4
*Wellcome Trust Centre for the Study of Molecular Mechanisms in Disease, University of Cambridge, Addenbrookes Hospital, Hills Road, Cambridge CB2 2XY, U.K.
4To whom correspondence should be addressed (e-mail hd162@cam.ac.uk).
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Publisher: Portland Press Ltd
Received:
July 19 2000
Revision Received:
November 01 2000
Accepted:
November 20 2000
Online ISSN: 1470-8728
Print ISSN: 0264-6021
The Biochemical Society, London © 2001
2001
Biochem J (2001) 353 (3): 655–661.
Article history
Received:
July 19 2000
Revision Received:
November 01 2000
Accepted:
November 20 2000
Citation
Paula E. ROW, Barbara J. REAVES, Jan DOMIN, J. Paul LUZIO, Howard W. DAVIDSON; Overexpression of a rat kinase-deficient phosphoinositide 3-kinase, Vps34p, inhibits cathepsin D maturation. Biochem J 1 February 2001; 353 (3): 655–661. doi: https://doi.org/10.1042/bj3530655
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