dictyNews
Electronic Edition
Volume 47, number 11
May 28, 2021

Please submit abstracts of your papers as soon as they have been
accepted for publication by sending them to [log in to unmask]
or by using the form at
http://dictybase.org/db/cgi-bin/dictyBase/abstract_submit.

Back issues of dictyNews, the Dicty Reference database and other
useful information is available at dictyBase - http://dictybase.org.

Follow dictyBase on twitter:
http://twitter.com/dictybase


=========
Abstracts
=========


Aberrant autophagy impacts growth and multicellular development 
in a Dictyostelium knockout model of CLN5 disease

Meagan D. McLaren,  Sabateeshan Mathavarajah,  William D. Kim, 
Shyong Q. Yap and Robert J. Huber


Frontiers in Cell and Developmental Biology, accepted

Mutations in CLN5 cause a subtype of neuronal ceroid lipofuscinosis 
(NCL) called CLN5 disease. While the precise role of CLN5 in NCL 
pathogenesis is not known, recent work revealed that the protein has 
glycoside hydrolase activity. Previous work on the Dictyostelium 
discoideum homolog of human CLN5, Cln5, revealed its secretion 
during the early stages of development and its role in regulating cell 
adhesion and cAMP-mediated chemotaxis. Here, we used 
Dictyostelium to examine the effect of cln5-deficiency on various 
growth and developmental processes during the life cycle. During 
growth, cln5- cells displayed reduced cell proliferation, cytokinesis, 
viability, and folic acid-mediated chemotaxis. In addition, the growth 
of cln5- cells was severely impaired in nutrient-limiting media. Based 
on these findings, we assessed autophagic flux in growth-phase cells 
and observed that loss of cln5 increased the number of 
autophagosomes suggesting that the basal level of autophagy was
 increased in cln5- cells. Similarly, loss of cln5 increased the amounts 
of ubiquitin-positive proteins. During the early stages of multicellular 
development, the aggregation of cln5- cells was delayed and loss of 
the autophagy genes, atg1 and atg9, reduced the extracellular amount 
of Cln5. We also observed an increased amount of intracellular Cln5 
in cells lacking the Dictyostelium homolog of the human glycoside 
hydrolase, hexosaminidase A (HEXA), further supporting the glycoside 
hydrolase activity of Cln5. This observation was also supported by 
our finding that CLN5 and HEXA expression are highly correlated in 
human tissues. Following mound formation, cln5- development was 
precocious and loss of cln5 affected spore morphology, germination, 
and viability. When cln5- cells were developed in the presence of 
the autophagy inhibitor ammonium chloride, the formation of 
multicellular structures was impaired, and the size of cln5- slugs 
was reduced relative to WT slugs. These results, coupled with the 
aberrant autophagic flux observed in cln5- cells during growth, 
support a role for Cln5 in autophagy during the Dictyostelium life 
cycle. In total, this study highlights the multifaceted role of Cln5 
in Dictyostelium and provides novel insight into the pathological 
mechanisms that may underlie CLN5 disease.


submitted by: Robert Huber [[log in to unmask]]
=======================================================
[End dictyNews, volume 47, number 11]