Effect of pH and zinc availability on Pac C processing in Aspergillus fumigatus

Ref ID: 19588

Author:

H Toledo1*, R Vicentefranqueira1, F Leal1, JA Calera1

Author address:

1Instituto de Biologí­a Funcional y Genómica, Universidad de Salamanca / CSIC, Salamanca, Spain

Full conference title:

6th Advances Against Aspergillosis 2014

Abstract:

Purpose:
The zinc adquisition has been proven to be an essential trait for Aspergillus fumigatus virulence. This
function relies on the alkaline zinc transporter ZrfC, which is required for optimal fungal growth
under alkaline zinc-limiting conditions. The expression of zrfC is strongly induced by ZafA under
alkaline zinc-limiting conditions because PacC, which regulates pH homeostasis in Aspergillus,
modulates somehow the ZafA transcriptional activation activity. In addition, our previous work
suggested that the repression of zrfC under acidic zinc-limiting conditions was PacC-dependent,
thus suggesting a novel function for PacC that, until now, has been proposed to be inactive in acidic
media.
The metabolic regulation by PacC has been widely described in A. nidulans, where is produced in an
inactive form (called p72) and then proteolized by a two-step mechanism to generate the active form
of the protein (called p27). Thus, as a first approach to investigate the PacC-mediated repression of
“œalkaline” genes such as zrfC, we tested whether the activation of the Af-PacC protein was as that
most widely accepted for An-PacC.
Methods:
To afford these experiments we constructed strains of A. fumigatus that express a Myc-tagged PacC
wild-type protein (Af-PacCwt) and Myc-tagged PacC mutant versions that mimic the growth of the
wild type at both acid (Af-PacCacid) and alkaline pH (Af-PacCalkaline). The growth capacity of these
mutant strains was tested under acidic and alkaline conditions and their defect on gene expression
was analyzed by northern blot using the zrfB (an “œacidic” gene) and zrfC (an “œalkaline” gene) genes
as probes. Afterwards, we analyzed by western-blot the processing pattern of the Myc-tagged PacC
proteins from all strains cultured under acidic and alkaline zinc-limiting conditions.
Results:
We observed that An-PacC was processed as expected according to previous studies, although some
processing was readily observed the in acidic defined media. In contrast, Af-PacCwt was processed in
all conditions tested regardless of pH and zinc availability, although processing occurred at a larger
extent in alkaline media. Both the Af-PacCacid and Af-PacCalkaline mutants processed partially under
all conditions tested.
Conclusion:
These results suggest that the Af-pal pH-signalling pathway might not influence Af-PacC processing
as directly as the An-pal pathway triggers An-PacC processing. Further investigations will be
required to understand the Af-pal route and its influence in Af-PacC function.

Abstract Number: 113

Conference Year: 2014

Link to conference website: http://www.AAA2014.org

New link: NULL

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