dictyNews
Electronic Edition
Volume 37, number 13
November 25, 2011

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Abstracts
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A single Beta adaptin contributes to AP1 and AP2 complexes and clathrin 
function in Dictyostelium

R. Thomas Sosa*, Michelle M. Weber *,Yujia Wen*, and Theresa J. O’Halloran


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The assembly of clathrin-coated vesicles is important for numerous 
cellular processes, including nutrient uptake and membrane organization. 
Important contributors to clathrin assembly are four tetrameric Assembly 
Proteins, also called Adaptor Proteins (AP’s), each of which contains a 
beta subunit. We identified a single beta subunit, named beta1/2, that 
contributes to both the AP1 and AP2 complexes of Dictyostelium. 
Disruption of the gene encoding beta1/2 resulted in severe defects in 
growth, cytokinesis, and development. Additionally, cells lacking beta1/2 
displayed profound osmoregulatory defects including the absence of 
contractile vacuoles and mislocalization of contractile vacuole markers. 
The phenotypes of beta1/2 were most similar to previously described 
phenotypes of clathrin and AP1 mutants, supporting a particularly 
important contribution of AP1 to clathrin pathways in Dictyostelium 
cells.  The absence of beta1/2 in cells led to significant reductions 
in the protein amounts of the medium-sized subunits of the AP1 and AP2 
complexes, establishing a role for the beta subunit in the stability of 
the medium subunits. Dictyostelium beta1/2 could resemble a common 
ancestor of the more specialized beta1 and beta2 subunits of the 
vertebrate AP complexes.  Our results support the essential contribution 
a single beta subunit to the stability and function AP1 and AP2 in a 
simple eukaryote. 


Submitted by Terry O'Halloran [[log in to unmask]]
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