Interactions of S100A2 and S100A6 with the Tetratricopeptide Repeat Proteins, Hsp90/Hsp70-organizing Protein and Kinesin Light Chain

Abstract

S100A2 and S100A6 interact with several target proteins in a Ca 2؉-regulated manner. However, the exact intracellular roles of the S100 proteins are unclear. In this study we identified Hsp70/ Hsp90-organizing protein (Hop) and kinesin light chain (KLC) as novel targets of S100A2 and S100A6. Hop directly associates with Hsp70 and Hsp90 through the tetratricopeptide (TPR) domains and regulates Hop-Hsp70 and Hop-Hsp90 complex formation. We have found that S100A2 and S100A6 bind to the TPR domain of Hop, resulting in inhibition of the Hop-Hsp70 and Hop-Hsp90 interactions in vitro. Although endogenous Hsp70 and Hsp90 interact with Hop in resting Cos-7 cells, but not with S100A6, stimulation of these cells with ionomycin caused a Hop-S100A6 interaction, resulting in the dissociation of Hsp70 and Hsp90 from Hop. Similarly, glutathione S-transferase pulldown and co-immunoprecipitation experiments revealed that S100A6 binds to the TPR domain of KLC, resulting in inhibition of the KLC-c-Jun N-terminal kinase (JNK)-interacting protein 1 (JIP-1) interaction in vitro. The transiently expressed JIP-1 interacts with KLC in resting Cos-7 cells but not with S100A6. Stimulation of these cells with ionomycin also caused a KLC-S100A6 interaction, resulting in dissociation of JIP-1 from KLC. These results strongly suggest that the S100 proteins modulate Hsp70-Hop-Hsp90 multichaperone complex formation and KLC-cargo interaction via Ca 2؉ -dependent S100 protein-TPR protein complex formation in vivo as well as in vitro. Moreover, we have shown that S100A2 and S100A6 interact with another TPR protein Tom70 and regulate the Tom70-ligand interaction in vitro. Thus, our findings suggest a new intracellular Ca 2؉

The Calcium-Dependent Interaction between S100B and the Mitochondrial AAA ATPase ATAD3A and the Role of This Complex in the Cytoplasmic Processing of ATAD3A

“…Consistent with this hypothesis, stress situations were necessary to reveal phenotypes associated with the S100 knockout in mice (11,14,33,56). Moreover, recent observations revealed a new function for the S100 protein family that included their ability to assist and regulate multichaperone complex-ligand interactions (41,50,51).…”

Hsp 70/Hsp 90 organizing protein as a nitrosylation target in cystic fibrosis therapy

“…Transnitrosation reactions are increasingly recognized to be important for cell signaling, and Hop interacts with and regulates the expression and function of a number of proteins that, themselves, are functionally S-nitrosylated. These include Hsp90 itself, protein von Hippel Lindau, S100A class proteins, and others (37)(38)(39)(40). Hop is believed to have an array of important cellular functions that could be affected by GSNO (23,24), an important consideration with regard to potential toxicities of S-nitrosothiol therapies.…”

S100 Proteins Modulate Protein Phosphatase 5 Function

“…Recombinant GSK-3␤ and protein kinase A were purchased from SignalChem and Promega, respectively. Human Hsp90 was prepared as described previously (5). Recombinant Tau protein was purchased from Enzo Life Sciences.…”

“…TPR 2 domains consist of repeated and conserved 34 amino acid sequences and interact with varieties of proteins, including Hsp90 anaphase-promoting complex, cell division cycle 37 (cdc37), and immunophilins (3,4). Recently, we demonstrated that S100A2 and S100A6 interacted with the TPR domains of Hsp70/Hsp90-organizing protein (Hop), kinesin light chain (KLC) and translocase of outer mitochondrial membrane 70 (Tom70) in a Ca 2ϩ -dependent manner, leading to dissociation of the Hsp90-Hop-Hsp70, KLC-c-Jun N-terminal kinase-interacting protein-1 (JIP-1) and Tom70-Hsps interactions (5). Further studies have revealed an interaction of S100A1 and S100A2 bound to FK506-binding protein 52 (FKBP52) and cyclophilin 40 (Cyp40), which contain a TPR domain, in the presence of Ca 2ϩ that led to inhibition of the Cyp40-Hsp90 and FKBP52-Hsp90 interactions (6).…”