Evidence against roles for phorbol binding protein Munc13-1, ADAM adaptor Eve-1, or vesicle trafficking phosphoproteins Munc18 or NSF as phospho-state-sensitive modulators of phorbol/PKC-activated Alzheimer APP ectodomain shedding

Ikin, Annat F. and Causevic, Mirsada and Pedrini, Steve and Benson, Lyndsey S. and Buxbaum, Joseph D. and Suzuki, Toshiharu and Lovestone, Simon and Higashiyama, Shigeki and Mustelin, Tomas and Burgoyne, Robert D. and Gandy, Sam (2007) Evidence against roles for phorbol binding protein Munc13-1, ADAM adaptor Eve-1, or vesicle trafficking phosphoproteins Munc18 or NSF as phospho-state-sensitive modulators of phorbol/PKC-activated Alzheimer APP ectodomain shedding. Molecular Neurodegeneration, 2. ISSN 1750-1326

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Abstract

Background: Shedding of the Alzheimer amyloid precursor protein (APP) ectodomain can be accelerated by phorbol esters, compounds that act via protein kinase C (PKC) or through unconventional phorbol-binding proteins such as Munc13-1. We have previously demonstrated that application of phorbol esters or purified PKC potentiates budding of APP-bearing secretory vesicles at the trans-Golgi network (TGN) and toward the plasma membrane where APP becomes a substrate for enzymes responsible for shedding, known collectively as α-secretase(s). However, molecular identification of the presumptive "phospho-state-sensitive modulators of ectodomain shedding" (PMES) responsible for regulated shedding has been challenging. Here, we examined the effects on APP ectodomain shedding of four phorbolsensitive proteins involved in regulation of vesicular membrane trafficking of APP: Munc13-1, Munc18, NSF, and Eve-1. Results: Overexpression of either phorbol-sensitive wildtype Munc13-1 or phorbol-insensitive Munc13-1 H567K resulted in increased basal APP ectodomain shedding. However, in contrast to the report of Roßner et al (2004), phorbol ester-dependent APP ectodomain shedding from cells overexpressing APP and Munc13-1 wildtype was indistinguishable from that observed following application of phorbol to cells overexpressing APP and Munc13-1 H567K mutant. This pattern of similar effects on basal and stimulated APP shedding was also observed for Munc18 and NSF. Eve-1, an ADAM adaptor protein reported to be essential for PKC-regulated shedding of pro-EGF, was found to play no obvious role in regulated shedding of sAPPα. Conclusion: Our results indicate that, in the HEK293 system, Munc13-1, Munc18, NSF, and EVE-1 fail to meet essential criteria for identity as PMES for APP.

Item Type: Article
Additional Information: 12 pages (page numbers not for citation purposes). Published: 9 December 2007.
Uncontrolled Keywords: Alzheimer amyloid precursor protein; APP; phorbol esters; protein kinase C; PKC; phorbol-binding proteins; shedding; trans-Golgi network; TGN; α-secretase(s); phospho-state-sensitive modulators of ectodomain shedding; PMES; phorbolsensitive proteins;
Subjects: R Medicine > R Medicine (General)
R Medicine > RC Internal medicine > RC0321 Neuroscience. Biological psychiatry. Neuropsychiatry
Divisions: ?? sch_biomed ??
Depositing User: Adina Dudau
Date Deposited: 06 Jun 2008 13:06
Last Modified: 09 Oct 2014 12:09
URI: http://repository.liv.ac.uk/id/eprint/673

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