PKA catalytic subunits are of great importance for Candida albicans glycogen storage

ROMINA GIACOMETTI; SUSANA PASSERON

Mar del Plata, Buenos Aires

Congreso; XLIII Reunión Anual SAIB; 2007

In C. albicans, regulation of MAPK and the cAMP/PKA transduction pathways is essential for growth, mycelial development, and glycogen storage. It is well known that S. cerevisiae cells with low PKA levels accumulate carbohydrates and become more resistant to heat and oxidative stress; on the opposite, cells with elevated kinase activity are unable to stock up reserves. We have addressed the participation of PKA subunits in glycogen metabolism in a set of C. albicans mutant strains deleted in PKA subunits genes. Previous results showed that strains devoid of one or both TPK1 alleles were defective in glycogen accumulation and mutants that lack the Tpk2p isoform, which represents 90% of total phosphotrasnferase activity, accumulated at least twice the amount than mutants harboring this isoform. We here report that triple mutant tpk2 TPK1/tpk1 BCY1/bcy1, which is unable to store glycogen, displayed the highest kinase activity at logarithmic phase, being the activity dramatically diminished at stationary phase. Our experiments suggest that glycogen absence in this strain is due in part to the unusual higher catalytic activity due to over-expression of the unique TPK1 isoform. We also studied the expression of different putative ORFs involved in glycogen metabolism. In a wild-type strain we found that these genes are differentially expressed during vegetative growth.