Phosphatidylinositol-4-phosphate 5-kinase activity is stimulated during temperature-induced morphogenesis in Candida albicans

Phosphoinositides are important lipid signalling molecules in eukaryotic cells. Phosphatidylinositol-4-phosphate 5-kinase (P14P5K) catalyses the production of phosphatidylinositol 4,5-bisphosphate (PIP2), which stimulates phospholipase D1 (PLD1) activity in mammalian and yeast cells. PLD1 catalyses the formation of phosphatidic acid (PA), which has been shown to activate P14P5Ks in mammalian and Saccharomyces cerevisiae cells. In the present study, P14P5K activity in the opportunistic pathogen Candida albicans was identified. A gene with significant sequence homology to the S. cerevisiae P14P5K was cloned and designated MSS4. This gene was demonstrated to encode a functional P14PSK by expression in S. cerevisiae. This enzyme was found to be membrane-associated and was stimulated by PA. Within the first 20 min after induction of polarized hyphal growth induced by a shift to elevated temperature, P14PSK activity increased 2-5-fold. This stimulation was not observed when hyphae were induced by a combination of elevated temperature and serum. A lack of PLD1 activity resulted in the loss of induction of P14PSK activity during the morphogenetic switch. Furthermore, the addition of propranolol attenuated the stimulation of P14PSK activity during morphogenesis. These results suggest that PA derived from PLD1 activity stimulates C. albicans P14P5K during the switch to the hyphal form under some conditions.