dictyNews
Electronic Edition
Volume 44, number 19
July 13, 2018
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Abstracts
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Expression of N471D strumpellin leads to defects in the endolysosomal
system
Lin Song1, Ramesh Rijal1,2, Malte Karow1, Maria Stumpf1, Oliver Hahn3,
Laura Park4, Robert Insall4, Rolf Schröder5, Andreas Hofmann6,7,
Christoph S. Clemen1,8, Ludwig Eichinger1
1Center for Biochemistry, Institute of Biochemistry I, Medical Faculty,
University of Cologne, Germany
2Department of Biology, Texas A&M University, USA
3Max Planck Institute for Biology of Ageing, Cologne, Germany
4CR-UK Beatson Institute for Cancer Research, Glasgow University, UK
5Institute of Neuropathology, University Hospital Erlangen, Erlangen,
Germany
6Structural Chemistry Program, Eskitis Institute, Griffith University, N75
Don Young Road, Nathan, Queensland 4111, Australia
7Faculty of Veterinary Science, The University of Melbourne, Parkville,
Victoria 3030, Australia
8Department of Neurology, Heimer Institute for Muscle Research,
University Hospital Bergmannsheil, Ruhr-University Bochum, Germany
Disease Models & Mechanisms, accepted
Hereditary Spastic Paraplegias (HSP) are genetically diverse and
clinically characterized by lower limb weakness and spasticity. The
N471D and several other point mutations of human strumpellin (Str),
a member of the WASH (Wiskott-Aldrich Syndrome Protein and SCAR
Homologue) complex, have been shown to cause HSP type 8 (SPG8).
To investigate the molecular functions of wild type and N417D Str, we
generated Dictyostelium Str¯ cells and ectopically expressed Strwt-GFP
or StrN471D-GFP in Str¯ and wt cells. Overexpression of both proteins
apparently caused a defect in cell division as we observed a clear
increase in multinucleate cells. Real time PCR analyses revealed no
transcriptional changes in WASH complex subunits in Str¯ cells, but
Western blots showed a two-fold decrease in the SWIP subunit. GFP-trap
experiments in conjunction with mass-spectrometric analysis revealed
many previously known as well as new Str interacting proteins and also
proteins that did no longer bind to StrN471D. On the cellular level, Str¯
cells displayed defects in cell growth, phagocytosis, macro-pinocytosis,
exocytosis and lysosomal function. Expression of Strwt-GFP in Str¯ cells
rescued all observed defects. In contrast, expression of StrN471D-GFP
could not rescue lysosome morphology and exocytosis of indigestible
material. Our results underscore a key role for the WASH complex and
its core subunit Str in the endo-lysosomal system and highlight the
fundamental importance of the Str N471 residue for maintaining
lysosome morphology and dynamics. Our data indicate that the SPG8-
causing N471D mutation leads to a partial loss of Strumpellin function in
the endo-lysosomal system.
submitted by: Ludwig Eichinger [[log in to unmask]]
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[End dictyNews, volume 44, number 19]
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