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Published 24 December 2001. doi:10.1083/jcb.200108152
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© The Rockefeller University Press, 0021-9525/2001/12/1251 $5.00
The Journal of Cell Biology, Volume 155, Number 7, December 24, 2001 1251-1264


Article

Human VPS34 is required for internal vesicle formation within multivesicular endosomes

C.E. Futter1, L.M. Collinson2, J.M. Backer3 and C.R. Hopkins2

1 Institute of Ophthalmology, University College London, London EC1V 9EL, United Kingdom
2 Imperial College of Science and Technology, London SW7 2AS, United Kingdom
3 Department of Molecular Pharmacology, Albert Einstein College of Medicine, New York, NY 10461

Address correspondence to Colin Hopkins, Dept. of Biochemistry, Imperial College of Science and Technology, London SW7 2AS, UK. Tel.: 44-207-594-5329. Fax: 44-207-225-0960. E-mail: colinhopkins{at}compuserve.ac.uk

After internalization from the plasma membrane, activated EGF receptors (EGFRs) are delivered to multivesicular bodies (MVBs). Within MVBs, EGFRs are removed from the perimeter membrane to internal vesicles, thereby being sorted from transferrin receptors, which recycle back to the plasma membrane. The phosphatidylinositol (PI) 3'-kinase inhibitor, wortmannin, inhibits internal vesicle formation within MVBs and causes EGFRs to remain in clusters on the perimeter membrane. Microinjection of isotype-specific inhibitory antibodies demonstrates that the PI 3'-kinase required for internal vesicle formation is hVPS34. In the presence of wortmannin, EGFRs continue to be delivered to lysosomes, showing that their removal from the recycling pathway and their delivery to lysosomes does not depend on inward vesiculation. We showed previously that tyrosine kinase-negative EGFRs fail to accumulate on internal vesicles of MVBs but are recycled rather than delivered to lysosomes. Therefore, we conclude that selection of EGFRs for inclusion on internal vesicles requires tyrosine kinase but not PI 3'-kinase activity, whereas vesicle formation requires PI 3'-kinase activity. Finally, in wortmannin-treated cells there is increased EGF-stimulated tyrosine phosphorylation when EGFRs are retained on the perimeter membrane of MVBs. Therefore, we suggest that inward vesiculation is involved directly with attenuating signal transduction.

Key Words: EGF receptor; VPS34; endosome; lysosome; phosphatidylinositol 3'-kinase


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