Reversible amyloids of pyruvate kinase couple cell metabolism and stress granule disassembly

Abstract

Cells respond to stress by blocking translation, rewiring metabolism, and forming transient mRNP assemblies called stress granules (SGs). After stress release, re-establishing homeostasis requires energy-consuming processes. However, the molecular mechanisms whereby cells restore energy production to disassemble SGs and reinitiate growth after stress remain poorly understood. Here we show that, upon stress, the ATP-producing enzyme Cdc19 forms inactive amyloids, and that their rapid re-solubilization is essential to restore energy production and disassemble SGs. Cdc19 re-solubilization is initiated by the glycolytic metabolite fructose-1,6-bisphosphate (FBP), which directly binds Cdc19 amyloids and facilitates conformational changes that allow Hsp104 and Ssa2 chaperone recruitment. FBP then promotes Cdc19 tetramerization, which boosts its activity to further enhance ATP production and SG disassembly. Together, these results describe a molecular mechanism essential for stress recovery, which directly couples metabolism with SG dynamics via regulation of Cdc19 amyloids.

A conserved mechanism regulates reversible amyloids via pH-sensing regions

“…Interestingly, Cdc19 aggregates possess an amyloid structure, both in vivo and in vitro (Fig. 1A and 5, 7 ), and thus resemble irreversible, pathological inclusions found in several neurodegenerative diseases 7, 8 . Yet, Cdc19 amyloids are fully re-solubilized in cells within minutes after stress release.…”

“…1A and 5, 6 ). In its aggregated form, Cdc19 is inactive and resistant to stress-induced degradation, while re-solubilization restores its enzymatic activity and energy production 7 . Thus, rapid formation of Cdc19 aggregates shuts down glycolysis and preserves Cdc19 from degradation during stress, while fast aggregate disassembly is crucial to restore energy production and reactivate metabolism.…”

“…While this pH-regulation is critical, additional mechanisms cooperate to promote rapid amyloid disassembly in vivo . For example, disassembly of Cdc19 amyloids in yeast is triggered by binding to the allosteric regulator fructose-1,6-biphosphate (FBP), which in turn triggers a conformational change to recruit dedicated chaperones 7 . Since PKM2 but not PKM1 is allosterically activated by FBP 37 , it is likely that this mechanism also couples metabolism and PKM2 aggregation in mammalian cells.…”

“…Importantly, our results highlight a plausible role of reversible PKM2 aggregation in disease settings such as cancer. Indeed, several cancer cell types are characterized by strong upregulation of PKM2 expression, which is thought to favour cancer metabolism and contribute to the Warburg effect, while deletion of PKM2 has been shown to slow tumor growth 7 . Interestingly, it was recently reported that PKM2 activity is not necessary for cancer cell proliferation, which may rather be driven by the inactive state of PKM2, while non-proliferating tumor cells require active pyruvate kinase 30 .…”

Amyloid Fragmentation and Disaggregation in Yeast and Animals

“…Amyloidogenic domains of more than ten other proteins form prions when fused to the Sup35 functional domain, though the propagation in a prion mode was not shown for these proteins on their own [ 17 ]. Transient prion-like amyloids can be induced by heat stress [ 19 , 20 ], and non-heritable functional amyloids called mnemons have been shown to mediate yeast cellular memory [ 21 ].…”