Defense against Protein Carbonylation by DnaK/DnaJ and Proteases of the Heat Shock Regulon

Abstract

Protein carbonylation is an irreversible oxidative modification that increases during organism aging and bacterial growth arrest. We analyzed whether the heat shock regulon has a role in defending Escherichia coli cells against this deleterious modification upon entry into stationary phase. Providing the cell with ectopically elevated levels of the heat shock transcription factor, sigma32, effectively reduced stasis-induced carbonylation. Separate overproduction of the major chaperone systems, DnaK/DnaJ and GroEL/GroES, established that the former of these is more important in counteracting protein carbonylation. Deletion of the heat shock proteases Lon and HslVU enhanced carbonylation whereas a clpP deletion alone had no effect. However, ClpP appears to have a role in reducing protein carbonyls in cells lacking Lon and HslVU. Proteomic immunodetection of carbonylated proteins in the wild-type, lon, and hslVU strains demonstrated that the same spectrum of proteins displayed a higher load of carbonyl groups in the lon and hslVU mutants. These proteins included the beta-subunit of RNA polymerase, elongation factors Tu and G, the E1 subunit of the pyruvate dehydrogenase complex, isocitrate dehydrogenase, 6-phosphogluconate dehydrogenase, and serine hydroxymethyltranferase.

Metabolite and transcriptome analysis of Campylobacter jejuni in vitro growth reveals a stationary-phase physiological switch

“…Protein damage in the form of carbonylation and disulphide bond formation is known to accumulate in E. coli stationary-phase cultures (Dukan & Nystrom, 1998). Heat-shock proteins are induced during stationary phase in this organism via the rpoH-encoded alternative sigma factor (Jenkins et al, 1991), and the action of DnaK/DnaJ and GroEL/GroES has been shown to protect against such damage through stabilization of polypeptides and assisting in their folding (Fredriksson et al, 2005;Siegenthaler & Christen, 2005;Tang et al, 2006). Although C. jejuni lacks any homologue of rpoH, the stationary-phase induction of heat shock genes may represent a similar response to protein damage, albeit regulated by a different mechanism.…”

Targeted Protein Degradation by Salmonella under Phagosome-mimicking Culture Conditions Investigated Using Comparative Peptidomics

“…These extensions are probably structurally disordered when unbound to polynucleotides because they are disproportionately detected by proteome-wide predictions of regions of intrinsic structural disorder (45,46). Lon is known to target defective proteins (47)(48)(49)(50)(51), probably because its unfoldase can process proteins that contain intrinsically disordered a These peptidomic samples are described in the Fig. 4 legend.…”

“…4, dnaK (33,50,65) and hns (33,66), are known to be carbonylated in response to starvation, and it is possible that they are subsequently targeted for proteolysis. Although Lon is the major protease of aberrant proteins in bacteria (47)(48)(49)(50)(51), ClpABPX (49 -51, 67), HslUV (50), and HtrA (49, 68) also have important roles. Therefore, two modes of protein degradation are likely upregulated by phagocytosed Salmonella, PolyP/Lon-dependent directed proteolysis of ribosomal proteins and ClpABPX/HslUV/ HtrA/Lon proteolysis of defective stress response factors.…”

Vieillissement : la chimie d’une horloge biologique flexible

“…Toutes les protéines ne sont pas égales face aux altérations provoquées par les espèces réactives d'oxygène (ROS) [3,4]. Dans la population humaine, les protéines vitales les plus susceptibles à l'oxydation représenteraient différents « maillons faibles », dont l'atteinte se manifeste au fur et à mesure que l'individu avance en âge.…”

“…Une des causes du vieillissement cellulaire est l'usure de ces systèmes de réparation et de renouvellement moléculaires qui se répercute sur la qualité du protéome entier. Or, ces systèmes -et notamment les protéines chaperons qui constituent un système de protection plus que de réparation -sont composés de protéines vulnérables, sensibles aux altérations chimiques comme l'oxydation [3,4]. Un cercle vicieux s'installe alors : l'oxydation des chaperons entraîne le mauvais repliement des protéines, leur oxydation [3,5], et donc une synthèse inefficace ne faisant qu'accroître l'oxydation [5], etc.…”