Chaperone proteins are involved in all aspects of proteostasis including protein synthesis, translocation, folding, and degradation. Moreover, many of them are involved in moonlighting activities such as apoptosis. Most chaperones have been studied extensively for more than three decades and much has become known about their structural properties and mechanisms of action. Nevertheless, many questions related to the interactions of chaperones with their clients remain open and are the focus of this Research Topic.
The identification of the set of clients of a chaperone system is a prerequisite for understanding its biological function and addressing questions related to its mechanism of client recognition and specificity. There has been little consensus, however, between different studies aimed at identifying the list of clients of certain chaperone systems as in, for example, the cases of CCT/TRiC (5-7) and GroEL. Such discrepancies could potentially be informative if their sources were better understood.
The client lists of other chaperone systems are still not well established, as in the case of the bacterial hsp90 (10) where certain organelle-specific chaperones and chaperone homologs that co-exist in the same cellular compartment. Given the lists of clients it is of great interest to understand what distinguishes them from non-clients. Binding motifs have been identified for some chaperone families, such as hsp70, but not for other chaperone families, such as the chaperonins and hsp90. In the case of the chaperonins, client binding appears to be governed mostly by kinetic partitioning between folding, aggregation, and chaperone binding. Client specificity can also be encoded by co-chaperones and affected by translation dynamics and competition between chaperones.
Finally, there is a host of intriguing questions related to the impact of chaperones on protein evolution, and vice versa. For example, can new proteins that arise due to gene duplication or horizontal gene transfer displace existing clients or must they be chaperone-independent? Do proteins in an organism that lacks a certain chaperone system (e.g. chaperonins in certain mollicutes) become dependent on other chaperone systems or evolve to become chaperone-independent? More generally, do chaperones potentiate genetic variation only of their clients, or more widely? As its title indicates, this Research Topic aims at highlighting various issues related to the interactions of chaperones with their clients. Such issues have received somewhat less attention than mechanistic aspects of their function despite their essential physiological importance.
The key questions we aim to discuss in the context of client proteins of chaperones include (but are not limited to) the following:
• Identifying the sets of clients of the different chaperone systems
• Determining the features which distinguish clients from non-clients
• Elucidating the biophysical and structural basis of client binding
• Revealing the extent of chaperone-client co-evolution and its effect on selection
Chaperone proteins are involved in all aspects of proteostasis including protein synthesis, translocation, folding, and degradation. Moreover, many of them are involved in moonlighting activities such as apoptosis. Most chaperones have been studied extensively for more than three decades and much has become known about their structural properties and mechanisms of action. Nevertheless, many questions related to the interactions of chaperones with their clients remain open and are the focus of this Research Topic.
The identification of the set of clients of a chaperone system is a prerequisite for understanding its biological function and addressing questions related to its mechanism of client recognition and specificity. There has been little consensus, however, between different studies aimed at identifying the list of clients of certain chaperone systems as in, for example, the cases of CCT/TRiC (5-7) and GroEL. Such discrepancies could potentially be informative if their sources were better understood.
The client lists of other chaperone systems are still not well established, as in the case of the bacterial hsp90 (10) where certain organelle-specific chaperones and chaperone homologs that co-exist in the same cellular compartment. Given the lists of clients it is of great interest to understand what distinguishes them from non-clients. Binding motifs have been identified for some chaperone families, such as hsp70, but not for other chaperone families, such as the chaperonins and hsp90. In the case of the chaperonins, client binding appears to be governed mostly by kinetic partitioning between folding, aggregation, and chaperone binding. Client specificity can also be encoded by co-chaperones and affected by translation dynamics and competition between chaperones.
Finally, there is a host of intriguing questions related to the impact of chaperones on protein evolution, and vice versa. For example, can new proteins that arise due to gene duplication or horizontal gene transfer displace existing clients or must they be chaperone-independent? Do proteins in an organism that lacks a certain chaperone system (e.g. chaperonins in certain mollicutes) become dependent on other chaperone systems or evolve to become chaperone-independent? More generally, do chaperones potentiate genetic variation only of their clients, or more widely? As its title indicates, this Research Topic aims at highlighting various issues related to the interactions of chaperones with their clients. Such issues have received somewhat less attention than mechanistic aspects of their function despite their essential physiological importance.
The key questions we aim to discuss in the context of client proteins of chaperones include (but are not limited to) the following:
• Identifying the sets of clients of the different chaperone systems
• Determining the features which distinguish clients from non-clients
• Elucidating the biophysical and structural basis of client binding
• Revealing the extent of chaperone-client co-evolution and its effect on selection