Biology subjects

Heinisch, J. J.

Publications and source records attributed to Heinisch, J. J..

4 recordsLinked to original sources

bioRxiv2025

The yeast phosphofructokinase β-subunit has ATP-dependent RNA unwinding activity and modulates cell cycle progression

Phosphofructokinase (PFK) is a rate-limiting glycolytic enzyme that also possesses an unexplored RNA binding activity. Here, we show that the - and {beta}-subunits of yeast PFK, encoded by PFK1 and PFK2, respectively, bind hundreds of mRNAs in cells, including ones coding for proteins involved in regulation of mitotic cell cycle. Pkf2p directly binds in a Mg-ATP-dependent manner to short GA-, UC-, AU- and U-rich motifs overrepresented in its mRNA targets. Strikingly, Pfk2p displays directional 5 - 3 double-stranded RNA unwinding activity not seen with Pfk1p. Furthermore, Pfk2p dynamically associates with ribosomes and promotes translation of cell cycle genes. Consequently, pfk2{Delta}, but not pfk1{Delta}, mutant cells show severely delayed G1/S phase transition which is independent of the enzymes glycolytic activity. Our results uncovered a hidden function for the Pfk2 subunit as a translational activator of mitotic cell cycle gene transcripts possibly through energy-dependent RNA unwinding activity.

molecular biology↗

bioRxiv2024

The Small GTPase Rho5 - Yet Another Player in Yeast Glucose Signaling

The small GTPase Rho5 has been shown to be involved in regulating the Bakers yeast response to stress on the cell wall, high medium osmolarity, and reactive oxygen species. These stress conditions trigger a rapid translocation of Rho5 and its dimeric GDP/GTP exchange factor (GEF) to the mitochondrial surface, which was also observed upon glucose starvation. We here show that rho5 deletions affect carbohydrate metabolism both at the transcriptomic and the proteomic level, in addition to cell wall and mitochondrial composition. Epistasis analyses with deletion mutants in components of the three major yeast glucose signaling pathways indicate a primary role of Rho5 upstream of the Ras2 GTPase in cAMP-mediated protein kinase A signaling. We also observed an inhibitory role of Rho5 on respiratory capacity, which may be explained by its role in mitophagy.

molecular biology↗

bioRxiv2022

Tau and α-synuclein shape microtubule organization and microtubule-dependent transport in neuronal dendrites

Tau and -synuclein are major players in neurodegenerative diseases, but their physiological role, particularly in dendrites, is poorly understood. Here we show that, surprisingly, lack of tau protein induces the development of a more elaborate dendritic arbor of hippocampal pyramidal cells in organotypic tissue. Using high-speed volumetric lattice light-sheet microscopy and single particle tracking, we found a more directional KIF1A-mediated transport in dendrites of Tau KO cells. Increased transport processivity correlated with longer and straighter dendritic microtubules as revealed by three-dimensional super-resolution microscopy of cultured hippocampal neurons. Unbiased mass spectrometric analysis of tissue showed highly increased expression of -synuclein in Tau KO hippocampi. Overexpression of -synuclein mimicked the transport characteristics observed in Tau KO cells. Our data indicate that tau and -synuclein shape microtubule-dependent transport in neuronal dendrites, thereby promoting dendritic arborization during maturation. Furthermore, the data demonstrate that transport efficiency and length and straightness of microtubules are correlated.

neuroscience↗

bioRxiv2020

Uptake of endogenous serine is important to maintain sphingolipid homeostasis in Saccharomyces cerevisiae

Sphingolipids are abundant and essential molecules in eukaryotes that have crucial functions as signaling molecules and as membrane components. Sphingolipid biosynthesis starts in the endoplasmic reticulum with the condensation of serine and palmitoyl-CoA. Sphingolipid biosynthesis is highly regulated to maintain sphingolipid homeostasis. Even though, serine is an essential component of the sphingolipid biosynthesis pathway, its role in maintaining sphingolipid homeostasis has not been precisely studied. Here we show that serine uptake is an important factor for the regulation of sphingolipid biosynthesis in Saccharomyces cerevisiae. Using genetic experiments, we find the broad-specificity amino acid permease Gnp1 to be important for serine uptake. We confirm these results with serine uptake assays in gnp1{Delta} cells. We further show that uptake of exogenous serine by Gnp1 is important to maintain cellular serine levels and observe a specific connection between serine uptake and the first step of sphingolipid biosynthesis. Using mass spectrometry-based flux analysis, we further observed imported serine as the main source for de novo sphingolipid biosynthesis. Our results demonstrate that yeast cells preferentially use the uptake of exogenous serine to regulate sphingolipid biosynthesis. Our study can also be a starting point to analyze the role of serine uptake in mammalian sphingolipid metabolism. Author SummarySphingolipids (SPs) are membrane lipids globally required for eukaryotic life. In contrast to other lipid classes, SPs cannot be stored in the cell and therefore their levels have to be tightly regulated. Failure to maintain sphingolipid homeostasis can result in pathologies including neurodegeneration, childhood asthma and cancer. However, we are only starting to understand how SP biosynthesis is adjusted according to need. In this study, we use genetic and biochemical methods to show that the uptake of exogenous serine is necessary to maintain SP homeostasis in Saccharomyces cerevisiae. Serine is one of the precursors of long chain bases in cells, the first intermediate of SP metabolism. Our results suggest that the uptake of serine is directly coupled to SP biosynthesis at ER-plasma membrane contact sites. Overall, our study identifies serine uptake as a novel regulatory factor of SP homeostasis. While we use yeast as a discovery tool, these results also provide valuable insights into mammalian SP biology especially under pathological conditions.

genetics↗