N-Acetyl-D-glucosamine-induced germ tube formation in Candda albicans at 37°C was accompanied by an increase in the rate of protein phosphorylation. The calmodulin antagonist trifluoperazine and the Ca2+ ionophore A23187, which inhibited germ tube formation, also reduced the rate of phosphorylation. The rate of phosphorylation was also reduced when cells were incubated at 25 "C, which favoured yeast-phase growth. Twodimensional SDS-PAGE analysis of phosphoproteins from germ-tube-forming and yeast cells revealed two germtube-specific and three yeast-specific phosphoproteins. Germ tubes and hyphae had more calmodulin activity than yeast cells, irrespective of the germ-tube-inducing condition used. As a first step towards understanding the inhibitory effect of trifluoperazine on germ tube formation, calmodulin from C. albicans was purified to homogeneity. It was heat stable, and displayed a pronounced Ca2+-induced shift in electrophoretic mobility.

No abstract

A calmodulin inhibitor, trifluoperazine (TFP), can block yeast‐to‐germ‐tube morphogenesis of Candida albicans induced by N‐acetyl‐d‐glucosamine at 37°C. Furthermore, the ionophore A23187 can also block germ tube formation, which can be reversed by Ca2+. This indicates the possible involvement of calcium and calmodulin in morphogenesis of C. albicans. During germ tube formation, there is a progressive increase in the rate of protein phosphorylation, which is completely absent in non‐germinating cells (yeast form). Trifluoperazine can also inhibit this phosphorylation indicating that protein phosphorylation may also be involved in this process.

A cyclic AMP-independent protein kinase which phosphorylates casein was purified to homogeneity from Candida albicans by affinity and ion-exchange chromatography. This protein kinase exhibits maximal activity with casein as substrate and is not stimulated by cyclic AMP or cyclic GMP. The Mr of the purified enzyme is 115,000, as determined by h.p.l.c. It migrates as a single band on gel electrophoresis and has three non-identical subunits, of Mr 44,000, 28,500 and 26,000, as determined by SDS/polyacrylamide-gel electrophoresis. This enzyme is insensitive to heparin, but is inhibited by polyamines. Furthermore, it is sensitive to thermal denaturation and to thiol reagents.

Background: Understanding cellular mechanism of communication is the main goal of systems biology. Unicellular yeasts are effective model to understand the molecular interactions that generate cell polarity induced by external inputs. The mechanisms of many extracellular stimuli are induced by complexes of cell surface receptors, G proteins. The mechanisms of many extracellular stimuli are induced by complexes of cell surface receptors, G proteins and mitogen activated protein (MAP) kinase complexes. Many components, their interrelationships, and their regulators of these mechanisms were initially identified in yeast. A complex web of sensing mechanisms and cooperation among signaling networks such as a cyclic adenosine monophosphate dependent protein kinase, mitogen-activated protein kinase cascade and 5-adenosine monophosphate activated protein kinase induce various changes in physiology, cell polarity, cell cycle progression and gene expression to achieve differentiation. Ras-cAMP pathway explained in yeast model with signalling function of the oncogenic mammalian Ras protein. So studies on yeast cells may enlighten some underlying mechanism which will be beneficial to understand the mechanisms of disease.