dictyNews
Electronic Edition
Volume 46, number 5
February 21, 2020

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Abstracts
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Mfsd8 localizes to endocytic compartments and influences the secretion
of Cln5 and cathepsin D in Dictyostelium 


Robert J. Huber, Sabateeshan Mathavarajah, Shyong Quan Yap


Department of Biology, Trent University, Peterborough, Ontario, Canada


Cellular Signalling, in press

The neuronal ceroid lipofuscinoses (NCLs) are a family of 
neurodegenerative diseases that affect people of all ages and ethnicities, 
yet many of the associated genes/proteins are not well characterized. 
Mutations in MFSD8 (major facilitator superfamily domain-containing 8) 
cause an infantile form of NCL referred to as CLN7 disease. In this study, 
we revealed the localization and binding partners of an ortholog of human 
MFSD8 (Mfsd8) in the social amoeba Dictyostelium discoideum. Putative
lysosomal targeting motifs are conserved in Dictyostelium Mfsd8, as are 
several residues mutated in CLN7 disease patients. Mfsd8 tagged with 
GFP localizes to endocytic compartments, which includes acidic 
intracellular vesicles and late endosomes. We pulled-down GFP-Mfsd8 
and used mass spectrometry to reveal the Mfsd8 interactome during 
Dictyostelium growth and starvation. Among the identified hits were the 
Dictyostelium ortholog of human cathepsin D (CtsD), as well as proteins 
linked to the functions of the CLN3 (Cln3) and CLN5 (Cln5) orthologs in 
Dictyostelium. To study the function of Mfsd8, we validated a publically 
available mfsd8- cell line (GWDI Project) and then used this knockout cell 
line to show that Mfsd8 influences the secretion of Cln5 and CtsD. This 
information is then integrated into an emerging model describing the 
molecular networking of NCL proteins in Dictyostelium. In total, this study 
identifies Dictyostelium as a new model system for studying CLN7 disease.


submitted by:  Robert Huber  [[log in to unmask]]
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