Characterization of Plasmodium falciparum co-chaperone p23: its intrinsic chaperone activity and interaction with Hsp90

Abstract

It is well known that the co-chaperone p23 regulates Hsp90 chaperone activity in protein folding. In Plasmodium falciparum, a putative p23 (Pfp23) has been identified through genome analysis, but its authenticity has remained unconfirmed since co-immunoprecipitation experiments failed to show its interaction with P. falciparum Hsp90 (PfHsp90). Thus, recombinant Pfp23 and PfHsp90 proteins purified from expressed clones were used in this study. It was clear that Pfp23 exhibited chaperone activity by virtue of its ability to suppress citrate synthase aggregation at 45 degrees C. Pfp23 was also shown to interact with PfHsp90 and to suppress its ATPase activity. Analyses of modeled Pfp23-PfHsp90 protein complex and site-directed mutagenesis further revealed strategically placed amino acid residues, K91, H93, W94 and K96, in Pfp23 to be crucial for binding PfHsp90. Collectively, this study has provided experimental evidence for the inherent chaperone function of Pfp23 and its interaction with PfHsp90, a sequel widely required for client protein activation.

Casein kinase 1.2 over expression restores stress resistance to Leishmania donovani HSP23 null mutants

“…P23 is a known co-chaperone of HSP90 and binds to the middle domain of HSP90 with a higher affinity for the ATP-bound state. This interaction was shown to temporarily stabilise the closed conformation of HSP90 and at the same time slowing the ATPase cycle [79][80][81][82][83][84] . Such an inhibitory effect on the HSP90 ATPase activity was also described for P23 and, to a lesser degree, for HSP23 in Leishmania braziliensis 85 .…”

Co-chaperones of Hsp90 inPlasmodium falciparumand their concerted roles in cellular regulation

“…Subsequent characterization study validated the role of Pfp23 as a co-chaperone of PfHsp90. Pfp23 was demonstrated to interact with PfHsp90 using GST pull-down assays and the association was dependent on the presence of ATP (Chua et al 2010). This observation is consistent with that reported in yeast where Sba1 (p23 homologue) preferentially interacts with Hsp82 (Hsp90 homologue) in the ATP-bound state (Sullivan et al 1997; Fang et al 1998).…”

“…This observation is consistent with that reported in yeast where Sba1 (p23 homologue) preferentially interacts with Hsp82 (Hsp90 homologue) in the ATP-bound state (Sullivan et al 1997; Fang et al 1998). The residues K91, H93, W94 and K96 in Pfp23 were further identified to be crucial for PfHsp90 interaction based on site-directed mutagenesis experiments (Chua et al 2010). The binding of Pfp23 was found to suppress the ATPase activity of PfHsp90, similar to that observed in the yeast and human homologues.…”

Estudo estrutural da co-chaperona Aha1 (Activator of Hsp90 ATPase 1) de Leishmania braziliensis e da sua ação sobre o ciclo funcional da Hsp90

“…Apesar disto, pouco se conhece a respeito de sua biologia, principalmente quando comparado a sistemas mais bem caracterizados, como levedura e humano. O conhecimento das co-chaperonas da Hsp90 de protozoários é ainda restrito: em P. falciparum, estudos foram realizados com as cochaperona p23 (Chua et al, 2010), Aha1 (Chua et al, 2012) e Hop (Gitau et al, 2012;Hatherley et al, 2015;Zininga et al, 2015); em T. gondii, a p23 foi investigada (Echeverria et al, 2010); e em L. braziliensis, trabalhos recentes caracterizaram as proteínas p23 e Aha1 (Koulov et al, 2010;Meyer et al, 2004;Retzlaff et al, 2010…”