Filamentation of asparagine synthetase in Saccharomyces cerevisiae

Abstract

Asparagine synthetase (ASNS) and CTP synthase (CTPS) are two metabolic enzymes crucial for glutamine homeostasis. A genome-wide screening in Saccharomyces cerevisiae reveal that both ASNS and CTPS form filamentous structures termed cytoophidia. Although CTPS cytoophidia were well documented in recent years, the filamentation of ASNS is less studied. Using the budding yeast as a model system, here we confirm that two ASNS proteins, Asn1 and Asn2, are capable of forming cytoophidia in diauxic and stationary phases. We find that glucose deprivation induces ASNS filament formation. Although ASNS and CTPS form distinct cytoophidia with different lengths, both structures locate adjacently to each other in most cells. Moreover, we demonstrate that the Asn1 cytoophidia colocalize with the Asn2 cytoophidia, while Asn2 filament assembly is largely dependent on Asn1. In addition, we are able to alter Asn1 filamentation by mutagenizing key sites on the dimer interface. Finally, we show that ASN1D330V promotes filamentation. The ASN1D330V mutation impedes cell growth in an ASN2 knockout background, while growing normally in an ASN2 wild-type background. Together, this study reveals a connection between ASNS and CTPS cytoophidia and the differential filament-forming capability between two ASNS paralogs.

Widespread remodeling of proteome solubility in response to different protein homeostasis stresses

“…The protein seen in five stresses, Asns, has been reported to form filaments in yeast under stress (65), suggesting it also is functionally remodeled in the stress response. When we consider the solubility changes in proteins found in, at least, three stresses in terms of KEGG pathways, we observed a clustering into core metabolic pathways of lipid metabolism, carbohydrate metabolism, nucleotide metabolism, amino acid metabolism, and energy metabolism (SI Appendix, Fig.…”

Forming cytoophidia prolongs the half-life of CTP synthase

“…Mounting evidence indicates that CTPS is not the only component of these filaments. We previously reported that inosine monophosphate dehydrogenase (IMPDH), the rate-limiting enzyme in de novo GTP biosynthesis, and asparagine synthetase (ASNS), an essential enzyme for biosynthesis of asparagine, can be assembled into similar filaments adjacent to the CTPS cytoophidium 20,21 . It may be that CTPS cytoophidia serves as a metabolic stabilizer and a cooperative platform for CTPS and many other metabolic enzymes.…”

Temperature-sensitive cytoophidium assembly in Schizosaccharomyces pombe

“…Several studies have shown that CTPS compartmentalizes into filamentous structures in various organisms, including bacteria, fruit fly, rat and human cells (Ingerson-Mahar et al., 2010; Liu, 2010; Noree et al., 2010; Carcamo et al., 2011; Chen et al., 2011). It has also been reported that CTPS filaments can be observed in budding yeast (Noree et al., 2010, 2014; Shen et al., 2016; Zhang et al., 2018). We have previously identified that CTPS forms cytoophidia in S. pombe (Zhang et al., 2014; Li et al., 2018).…”