dictyNews
Electronic Edition
Volume 40, number 24
September 19, 2014

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Abstracts
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PTEN Hopping on the Cell Membrane Is Regulated via a 
Positively-Charged C2 Domain

Masato Yasui, Satomi Matsuoka, Masahiro Ueda


PLoS Computational Biology, 10(9): e1003817.

PTEN, a tumor suppressor that is frequently mutated in a wide spectrum 
of cancers, exerts PI(3,4,5)P3 phosphatase activities that are regulated 
by its dynamic shuttling between the membrane and cytoplasm. Direct 
observation of PTEN in the interfacial environment can offer 
quantitative information about the shuttling dynamics, but remains 
elusive. Here we show that positively charged residues located in the 
Calpha2 helix of the C2 domain are necessary for the membrane localization 
of PTEN via stable electrostatic interactions in Dictyostelium discoideum. 
Single-molecule imaging analyses revealed that PTEN molecules moved 
distances much larger than expected had they been caused by lateral 
diffusion, a phenomenon we call "hopping." Our novel single-particle 
tracking analysis method found that the Calpha2 helix aids in regulating 
the hopping and stable-binding states. The dynamically established 
membrane localization of PTEN was revealed to be essential for 
developmental processes and clarified a fundamental regulation mechanism 
of the protein quantity and activity on the plasma membrane.


Submitted by Satomi Matsuoka [[log in to unmask]]
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Loss of Cln3 function in the social amoeba Dictyostelium discoideum 
causes pleiotropic effects that are rescued by human CLN3

Robert J. Huber*, Michael A. Myre†, Susan L. Cotman†

Center for Human Genetic Research, Massachusetts 
General Hospital, Harvard Medical School,
185 Cambridge Street, Boston, Massachusetts, USA 02114

* Corresponding author
† These authors contributed equally to the work


PLoS One, accepted

The neuronal ceroid lipofuscinoses (NCL) are a group of inherited, 
severe neurodegenerative disorders also known as Batten disease. 
Juvenile NCL (JNCL) is caused by recessive loss-of-function 
mutations in CLN3, which encodes a transmembrane protein that 
regulates endocytic pathway trafficking, though its primary 
function is not yet known. The social amoeba Dictyostelium 
discoideum is increasingly utilized for neurological disease 
research and is particularly suited for investigation of protein 
function in trafficking. Therefore, here we establish new 
overexpression and knockout Dictyostelium cell lines for JNCL 
research. Dictyostelium Cln3 fused to GFP localized to the 
contractile vacuole system and to compartments of the endocytic 
pathway. cln3- cells displayed increased rates of proliferation 
and an associated reduction in the extracellular levels and 
cleavage of the autocrine proliferation repressor, AprA. Mid- 
and late development of cln3- cells was precocious and cln3- 
slugs displayed increased migration. Expression of either 
Dictyostelium Cln3 or human CLN3 in cln3- cells suppressed the 
precocious development and aberrant slug migration, which were 
also suppressed by calcium chelation. Taken together, our 
results show that Cln3 is a pleiotropic protein that negatively 
regulates proliferation and development in Dictyostelium. This 
new model system, which allows for the study of Cln3 function 
in both single cells and a multicellular organism, together with 
the observation that expression of human CLN3 restores 
abnormalities in Dictyostelium cln3- cells, strongly supports 
the use of this new model for JNCL research.


Submitted by Robert Huber [[log in to unmask]]
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[End dictyNews, volume 40, number 24]