dictyNews
Electronic Edition
Volume 40, number 12
May 2, 2014

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Abstracts
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Xiong Liu, Shi Shu, Shuhua Yu, Duck-Yeon Lee, Grzegorz Piszczek, Marjan Gucek, 
Guanghui Wang and Edward D. Korn

Biochemical and biological properties of cortexillin III, a component of 
Dictyostelium DGAP1-cortexillin complexes


Molecular Biology of the Cell, accepted

Cortexillins I, II and III are members of the alpha-actinin/spectrin sub-family 
of Dictyostelium calponin homology proteins.  Unlike recombinant cortexillins 
I and II, which form homodimers as well as heterodimers in vitro, we find that 
recombinant cortexillin III is an unstable monomer but forms more stable 
heterodimers when co-expressed in E. coli with cortexillin I or II.  Expressed 
cortexillin III also forms heterodimers with both cortexillin I and II in vivo 
and the heterodimers complex in vivo with DGAP1, a Dictyostelium GAP protein.  
Binding of cortexillin III to DGAP1 requires the presence of either cortexillin 
I or II, i.e. cortexillin III binds to DGAP1 only as a heterodimer, and the 
heterodimers form in vivo in the absence of DGAP1.  Expressed cortexillin III 
co-localizes with cortexillins I and II in the cortex of vegetative amoebae, the 
leading edge of motile cells and the cleavage furrow of dividing cells.  
Co-localization of ctxIII and F-actin may require the heterodimer/DGAP1 complex.  
Functionally, cortexillin III may be a negative regulator of cell growth, 
cytokinesis, pinocytosis and phagocytosis as all are enhanced in cortexillin 
III-null cells.


Submitted by Edward D. Korn [edk@nih.gov]
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[End dictyNews, volume 40, number 12]