Trypanosoma bruceiJ protein 2 functionally cooperates with the cytosolic Hsp70.4 and Hsp70 proteins

Abstract

30The etiological agent of African trypanosomiasis, Trypanosoma brucei, has been identified to 31 possess an expanded and diverse group of heat shock proteins, that have been implicated in 32 cytoprotection, differentiation, and subsequently progression and transmission of the disease. 33 Heat shock protein 70 is a highly conserved and ubiquitous molecular chaperone that is 34 important in maintaining protein homeostasis in the cell. Its function is regulated by a wide 35 range of co-chaperones; and inhibition of these functions and interactions with co-chaperones 36 are emerging as potential therapeutic targets for numerous diseases. This study sought to 37 biochemically characterize the cytosolic Hsp70 and Hsp70.4 proteins and to investigate if they 38 form a functional partnership with the Type I J-protein, Tbj2. The cytosolic localisation of the 39 proteins was confirmed by accessing the TrypTag endogenous tagging microscopy database. 40Expression of TbHsp70 was shown to be heat inducible, whilst TbHsp70.4 was constitutively 41 expressed. The basal ATPase activities of TbHsp70.4 and TbHsp70 were stimulated by Tbj2. 42It was further determined that Tbj2 forms a functional partnership with TbHsp70 and 43 TbHsp70.4 as the J-protein was shown to stimulate the ability of both proteins to mediate the 44 refolding of chemically denatured β-galactosidase. This study provides further insight into this 45 important class of proteins which may contribute to the development of new therapeutic 46 strategies to combat African Trypanosomiasis. 47 48 49 50 51 52 53 54 3 55 Introduction 56 African trypanosomiasis, a neglected tropical disease, afflicts humans as well as domestic and 57 wild animals, and has a detrimental impact on socioeconomic development in sub-Saharan 58 Africa [1]. There is a need for the development of more effective and safer chemotherapies to 59 treat the disease, due to existing drug toxicity, growing parasite resistance and the lack of a 60 vaccine [2]. The Hsp70/J-protein chaperone machinery has been implicated to play an integral 61 role in the development, differentiation, and survival of protozoan parasites, as they transition 62 through the various stages of their life cycle [3]. In Leishmania and Trypanosoma cruzi, heat 63 shock proteins have been shown to play an essential role in stress-induced stage differentiation 64 and are important for disease progression and transmission [4-5], making this protein family 65 an attractive chemotherapeutic target. The completion of the Trypanosoma brucei (T. brucei) 66 genome has expedited transcriptome and proteome analyses and revealed that the extracellular 67 parasite has an expanded and diverse Hsp70 and J-protein complement, with the parasite 68 possessing cytosolic Hsp70 members that display atypical Hsp70 features [6]. 69 70 The Hsp70 protein family is ubiquitous and plays an integral role in protein quality control and 71 maintaining protein homeostasis under normal and stressful conditions [7-8]. Evolution has 72 given rise to multiple ...