Filamentation of Metabolic Enzymes in Saccharomyces cerevisiae

Qing-Ji Shen,Hakimi Kassim,Yong Huang,Hui Li,Jing Zhang,Guang Li,Peng-Ye Wang,Jun Yan,Fangfu Ye,Ji-Long Liu

doi:10.1016/j.jgg.2016.03.008

Abstract

Compartmentation via filamentation has recently emerged as a novel mechanism for metabolic regulation. In order to identify filament-forming metabolic enzymes systematically, we performed a genome-wide screening of all strains available from an open reading frame-GFP collection in Saccharomyces cerevisiae. We discovered nine novel filament-forming proteins and also confirmed those identified previously. From the 4159 strains, we found 23 proteins, mostly metabolic enzymes, which are capable of forming filaments in vivo. In silico protein-protein interaction analysis suggests that these filament-forming proteins can be clustered into several groups, including translational initiation machinery and glucose and nitrogen metabolic pathways. Using glutamine-utilising enzymes as examples, we found that the culture conditions affect the occurrence and length of the metabolic filaments. Furthermore, we found that two CTP synthases (Ura7p and Ura8p) and two asparagine synthetases (Asn1p and Asn2p) form filaments both in the cytoplasm and in the nucleus. Live imaging analyses suggest that metabolic filaments undergo sub-diffusion. Taken together, our genome-wide screening identifies additional filament-forming proteins in S. cerevisiae and suggests that filamentation of metabolic enzymes is more general than currently appreciated.

Highlights

Compartmentation of biological processes is a fundamental feature of the cell
Forming cytoophidia might serve as a complementary regulatory strategy for CTP synthase (CTPS) other than allosteric regulators or phosphorylation (Aughey et al, 2014a, 2014b)
Further study of the regulation of these filaments may answer questions such as whether filamentation is a common way of enzyme regulation, and whether filamentation is an indicator of a different form of cell metabolism

Summary

Introduction

Compartmentation of biological processes is a fundamental feature of the cell. One such way is to form membrane-bound organelles, which have been extensively appreciated in the past. In 2010, three groups independently described that the metabolic enzyme CTP synthase (CTPS) can form filamentous structures in bacteria, yeast and fruit flies (Ingerson-Mahar et al, 2010; Liu, 2010; Noree et al, 2010). These filaments have been termed as “cytoophidia” (meaning cellular snakes in Greek), “CTPS filaments”, or “cytoplasmic rods and rings”.

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Conclusion