Mitotic defects in fission yeast lipid metabolism ‘cut’ mutants are suppressed by ammonium chloride

Abstract

Fission yeast ‘cut’ mutants show defects in temporal coordination of nuclear division with cytokinesis, resulting in aberrant mitosis and lethality. Among other causes, the ‘cut’ phenotype can be triggered by genetic or chemical perturbation of lipid metabolism, supposedly resulting in shortage of membrane phospholipids and insufficient nuclear envelope expansion during anaphase. Interestingly, penetrance of the ‘cut’ phenotype in mutants of the transcription factor cbf11 and acetyl-coenzyme A carboxylase cut6, both related to lipid metabolism, is highly dependent on growth media, although the specific nutrient(s) affecting ‘cut’ occurrence is not known. In this study, we set out to identify the growth media component(s) responsible for ‘cut’ phenotype suppression in Δcbf11 and cut6–621 cells. We show that mitotic defects occur rapidly in Δcbf11 cells upon shift from the minimal EMM medium (‘cut’ suppressing) to the complex YES medium (‘cut’ promoting). By growing cells in YES medium supplemented with individual EMM components, we identified ammonium chloride, an efficiently utilized nitrogen source, as a specific and potent suppressor of the ‘cut’ phenotype in both Δcbf11 and cut6–621. Furthermore, we found that ammonium chloride boosts lipid droplet formation in wild-type cells. Our findings suggest a possible involvement of nutrient-responsive signaling in ‘cut’ suppression.

The phenomenon of lipid metabolism “cut” mutants

“…However, it remains an open question whether ammonium chloride rescues cut by directly affecting PL synthesis or whether it acts more indirectly by affecting processes unrelated to lipid metabolism but connected to mitotic progression. Interestingly, we found that the presence of ammonium chloride increases lipid droplet content in wild type S. pombe cells (Zach et al, ), which indicates that it can indeed affect lipid metabolism. Notably, the ned1 S627A/S629A mutant, which is unable to upregulate PL biosynthesis during mitosis, is not viable and cells are cut even in the presence of abundant ammonium chloride (Makarova et al, ).…”

“…Whereas in the complex yeast extract with supplements (YES) medium the incidence of cut mitoses is high in cut6–621 and cbf11∆ mutants, the mitotic defects are largely suppressed when mutant cells are grown in the Edinburgh minimal medium (EMM) defined medium, or upon genetic disruption of nutrient‐sensitive signaling pathways of protein kinase A (Pka1) and stress‐activated protein kinase (Sty1/Spc1; Převorovský et al, ; Převorovský et al, ). We have recently shown that the crucial suppressive component of EMM is ammonium chloride, a good nitrogen source, suggesting that nitrogen source availability and/or nitrogen‐dependent signaling play an important role in the successful progression through mitosis in S. pombe (Zach et al, ). However, it remains an open question whether ammonium chloride rescues cut by directly affecting PL synthesis or whether it acts more indirectly by affecting processes unrelated to lipid metabolism but connected to mitotic progression.…”

“…Strikingly, no cut phenotype has been reported for the mga2Δ mutant. Because the incidence of the cut phenotype in cbf11Δ cells is largely dependent on nutrient-sensing pathways (Převorovský et al, 2015), and cut in both cbf11Δ and cut6-621 mutants can be suppressed by altering growth media composition, particularly the nitrogen source (Převorovský et al, 2016;Zach et al, 2018), it is possible that the mga2Δ mutant might exert the cut phenotype under specific growth conditions, not tested so far. for Cut6/ACC in the ppc1 mutants (Nakamura et al, 2012).…”

Metabolism of phospholipids in the yeast Schizosaccharomyces pombe

“…The “cut” phenotype has been in this case ascribed to insufficient FA production and membrane PL supply during anaphase, when rapid expansion of the nuclear envelope takes place. Recently, it was observed that the cut6 mutant phenotype, together with the “cut” phenotype caused by the deletion of the transcription factor cbf11 , can be suppressed by supplementation of the growth medium with ammonium chloride (Zach et al, ). Cbf11 is a transcription factor which regulates the expression of several genes involved in lipid metabolism, including cut6 (Prevorovsky et al, ; Prevorovsky et al, ).…”

Analisis Molekular dan Transpor Ion Amonium Clorida

“…Reaksi yang terjadi, yaitu : NH3 +HCl NH4Cl ΔH= -175,7 kJ/mol Reaksi berlansung secara eksotermik, dan panas yang dibangkitkan yang digunakan untuk menguapkan sebagian besar air, ada ketika asam klorida (33)(34)(35)(36)(37) cair digunakan. Ammonium klorida (23,26,27,29) dapat dihasilkan lewat kristalisasi.…”