Polyphosphate Stabilizes Protein Unfolding Intermediates as Soluble Amyloid-like Oligomers

Abstract

Inorganic polyphosphate (polyP) constitutes one of the most conserved and ubiquitous molecules in biology. Recent work in bacteria demonstrated that polyP increases oxidative stress resistance by preventing stress-induced protein aggregation and promotes biofilm formation by stimulating functional amyloid formation. To gain insights into these two seemingly contradictory functions of polyP, we investigated the effects of polyP on the folding model lactate dehydrogenase. We discovered that the presence of polyP during the thermal unfolding process stabilizes folding intermediates of lactate dehydrogenase as soluble micro-β-aggregates with amyloid-like properties. Size and heterogeneity of the oligomers formed in this process were dependent on the polyP chain length, with longer chains forming smaller, more homogenous complexes. This ability of polyP to stabilize thermally unfolded proteins even upon exposure to extreme temperatures appears to contribute to the observed resistance of uropathogenic Escherichia coli toward severe heat shock treatment. These results suggest that the working mechanism of polyP is the same for both soluble and amyloidogenic proteins, with the ultimate outcome likely being determined by a combination of polyP chain length and the client protein itself. They help to explain how polyP can simultaneously function as general stress-protective chaperone and instigator of amyloidogenic processes in vivo.

Inorganic Polyphosphate Accumulation in Escherichia coli Is Regulated by DksA but Not by (p)ppGpp

“…3C), DksA is clearly not essential for detecting this specific stress condition. polyP synthesis is activated by a variety of stresses other than amino acid starvation (25,(27)(28)(29), and we are currently exploring the roles of (p)ppGpp and DksA in polyP synthesis in response to these other stress conditions.…”

“…Inorganic polyphosphate (polyP), a linear biopolymer composed of up to a thousand phosphoanhydride bond-linked phosphate monomers, is the key component of another, much less well understood general stress response pathway in bacteria (22)(23)(24)(25)(26). Bacteria from diverse phyla synthesize polyP in response to multiple stressors, including amino acid starvation, oxidative stress, heat shock, salt stress, and heavy metal exposure, and mutants lacking the ppk gene, which encodes the polyP-synthesizing kinase PPK, are highly sensitive to these and other stresses (25,(27)(28)(29)(30). The mechanisms by which polyP mediates bacterial stress resistance are not completely characterized, but in E. coli, polyP is known to act as a protein-stabilizing chaperone, as a metal chelator, and as a regulator of RNA polymerase and DNA polymerase IV activity, ribosomal translation fidelity, and transcription, including that of rpoS, which encodes the general stress response sigma factor S (3,25,27,28,(31)(32)(33)(34)(35)(36)(37).…”

A Stringent Analysis of Polyphosphate Dynamics in Escherichia coli

“…modulates aggregation of other proteins, including amyloidogenic proteins associated with human neurological disease (47)(48)(49). Intriguingly, polyP can also be added to the N-of lysine as a posttranslational modification called polyphosphorylation (26,(50)(51)(52).…”

Polyanions provide selective control of APC/C interactions with the activator subunit

“…Nucleic acids and polyphosphate exhibit chaperone-like properties, accelerate protein folding, and serve as anti-aggregation agents by solubilizing a variety of protein aggregates in vitro [34][35][36] . Long stretches of phosphate residues also inhibit polymerization of multimeric proteins and stabilize soluble structures 37,38 . Our work reveals that polyanions also influence the dynamics of APC/C-activator interactions, specifically disrupting APC/C-activator binding while leaving the multi-subunit APC/C core intact.…”