Mutational Analysis of Aspergillus fumigatus Calcineurin A reveals critical domains required for its function in vivo and targeting to the hyphal septum.

Praveen R Juvvadi, Jarrod R Fortwendel, Luise E Rogg, and William J Steinbach.

Author address: 

Department of Pediatrics, Division of Pediatric Infectious Diseases Duke University Medical Center, Durham NC, USA.


Calcineurin, a conserved calmodulin-dependent protein phosphatase, is a heterodimer consisting of the catalytic (CnaA) and the regulatory (CnaB) subunits. It is known to play key roles in virulence, growth and stress responses of pathogenic fungi. Critically understanding the calcineurin pathway and identifying the residues indispensible for calcineurin activity in vivo will pave way for devising new drug targets for combating Aspergillosis. We previously reported that CnaA localizes at the hyphal septum implicating its importance for septum formation and conidiophore development. By constructing the delta-cnaA delta-cnaB double mutant strain of A. fumigatus and utilizing the dual fluorescent labeling technique we provide evidence on colocalization of CnaA-GFP and mcherry-CnaB fusion proteins at the hyphal septum. Surprisingly, while the CnaB-GFP fusion protein mislocalized to the cytosol in the absence of of cnaA, cnaA still localized to the hyphal septum in the absence of cnaB. By site-directed point mutagenesis of several residues in the catalytic domain, CnaB binding helix, and the calmodulin binding domain of CnaA, we identify critical domains essential for its function in vivo apart from the absolute requirement of complexing with CnaB for its function at the hyphal septum.

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Full conference title: 

26th Fungal Genetics Conference
    • Fungal Genetics Conference 26th (2005)