Phosphoinositide-bis-phosphate is required for Saccharomyces cerevisiae invasive growth

Abstract

SummaryPhosphatidylinositol phosphates are important regulators of processes such as the cytoskeleton organization, membrane trafficking and gene transcription, which are all crucial for polarized cell growth. In particular, phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P 2 ] has essential roles in polarized growth as well as in cellular responses to stress. In the yeast Saccharomyces cerevisiae, the sole phosphatidylinositol-4-phosphate 5-kinase (PI4P5K) Mss4p is essential for generating plasma membrane PtdIns(4,5)P 2 . Here, we show that Mss4p is required for yeast invasive growth in low-nutrient conditions. We isolated specific mss4 mutants that were defective in cell elongation, induction of the Flo11p flocculin, adhesion and cell wall integrity. We show that mss4-f12 cells have reduced plasma membrane PtdIns(4,5)P 2 levels as well as a defect in its polarized distribution, yet Mss4-f12p is catalytically active in vitro. In addition, the Mss4-f12 protein was defective in localizing to the plasma membrane. Furthermore, addition of cAMP, but not an activated MAPKKK allele, partially restored the invasive growth defect of mss4-f12 cells. Taken together, our results indicate that plasma membrane PtdIns(4,5)P 2 is crucial for yeast invasive growth and suggest that this phospholipid functions upstream of the cAMP-dependent protein kinase A signaling pathway.

Role of Phosphatidylinositol Phosphate Signaling in the Regulation of the Filamentous-Growth Mitogen-Activated Protein Kinase Pathway

“…Failure of PM regulators to reach the PM may be expected to result in MAPK signaling defects. Previous studies have implicated PI signaling in the regulation of filamentous growth, particularly in C. albicans (72)(73)(74). Here, we posit that this connection can be explained, at least in part, at the level of the MAPK pathway.…”

“…A clear link between PIP signaling and the regulation of the filamentous-growth MAPK pathway has yet to be defined. Intriguingly, in C. albicans, steep PI(4,5)P2 gradients occur at hyphal tips and promote filamentous growth and invasion (72)(73)(74).…”

Cell polarization in budding and fission yeasts

“…This lipid has been shown to bind two exocyst subunits and septins as well as recruit a Rho1 GEF, PAK, and a Cdc42 effector (Audhya & Emr, ; He et al ., ; Orlando et al ., ; Takahashi & Pryciak, ; Zhang et al ., ; Bertin et al ., ). In budding yeast, PI(4,5)P 2 is enriched at sites of polarized growth including the bud, bud neck, and at the site of cell division during cytokinesis (Garrenton et al ., ; Guillas et al ., ) and at the site of cell division in fission yeast (Zhang et al ., ). It has been proposed that PI(4,5)P 2 is generated by the exocytic delivery of phosphatidylinositol to the plasma membrane and that this results in the activation of Cdc42 and regulation of the actin cytoskeleton (Yakir‐Tamang & Gerst, ).…”

Identification of a conserved 8 aa insert in the PIP5K protein in the Saccharomycetaceae family of fungi and the molecular dynamics simulations and structural analysis to investigate its potential functional role

“…The budding yeast Saccharomyces cerevisiae contains a single homolog of the PIP5K, which is referred to as the multicopy suppressor of stt4 mutation (MSS4) or PIP5K/MSS4. The PIP5K is a 90 kDa protein, which is primarily localized on the plasma membrane and it is required for diverse essential cellular processes, such as membrane trafficking, cell polarity, viability, morphogenesis, cytokinesis and actin cytoskeleton organization . Although the N‐terminal half of the PIP5K protein shows no sequence similarity to any protein outside of fungi, its C‐terminal half is homologous to the mammalian PIP5K and contains the well‐conserved catalytic kinase domain .…”