Regulation of chitin synthase activity in the dimorphic fungus Benjaminiella poitrasii by external osmotic pressure

Abstract

The effects of changes in external osmotic pressure on chitin synthase activity of a dimorphic fungus, Benjaminiella poitrasii, have been investigated. Mycelial and yeast cells incubated in medium of low osmolality (distilled water, 0 mOsm) for 10 min had 2-3-fold higher specific activities of native chitin synthase in mixed membrane preparations than cells that had been subjected to a high osmolality medium (1.2 M sorbitol in distilled water, 1612 mOsm). Cells suspended in media of different osmolalities for 10 min were also affected in the extent of germ tube formation. Germ tube formation was highest in cells incubated in low osmolality medium. The addition of protein phosphatase inhibitors (cyclosporin A, 1.2 micrograms/ml; cantharidin, 20 microM) abolished the effect of hypo-osmotic stress on chitin synthase activation of yeast mixed membrane preparations. The presence of protein kinase inhibitors (genistein, 40 micrograms/ml; H-7, 100 microM) and a Ca2+ channel blocker (verapamil, 50 microM) reduced chitin synthase activity to 50-60% of that observed in cells under hypo-osmotic shock. These inhibitors also inhibited germ tube formation. This suggests that chitin synthase activity and yeast hyphal morphogenesis are both subject to regulation by osmotic pressure, phosphorylation and calcium.

Influence of sorbitol on protein production and glycosylation and cell wall formation in Trichoderma reesei

“…In our study, we observed a significant decrease of chitin level in the cell wall of T. reesei grown with 1 M sorbitol, even though the total glucan level was more than twice lower than in the control. These results are in agreement with a study on the dimorphic fungus Benjaminiella poitrasii which, when grow in high osmolarity conditions, exhibited a decreased chitin synthase activity (Deshpande et al 1997).…”

The cell wall sensor Wsc1p is involved in reorganization of actin cytoskeleton in response to hypo‐osmotic shock in Saccharomyces cerevisiae

“…On the other hand, it is well known that in hypo‐osmotic challenged cells, as a consequence of influx of water, cells swell and Mpk1p is transiently activated. In addition, it has also been reported that chitin synthesis is stimulated in cells grown in hypotonic conditions with respect to hypertonic ones (Davenport et al , 1995; Deshpande et al , 1997; Munro et al , 1998; Popolo et al , 1997; Turchini et al , 2000). In addition, it has been recently found that in cells defective in β(1,3)‐glucan synthesis, loss of downregulation of the HOG pathway or deletion of the glycerol channel Fps1p are detrimental for growth (Lesage et al , 2004).…”

The PKC, HOG and Ca2+ signalling pathways co‐ordinately regulate chitin synthesis in Candida albicans

“…In S. cerevisiae , the HOG pathway is required for the response to CFW and mutants in several components of the pathway are resistant to CFW (Garcia‐Rodriguez et al ., 2000). In addition, changes in osmotic pressure have been shown to regulate chitin synthase activity in the dimorphic fungus Benjaminiella poitrasii suggesting the HOG pathway is involved in chitin regulation (Deshpande et al ., 1997).…”