Biology subjects

Baischew, A.

Publications and source records attributed to Baischew, A..

2 recordsLinked to original sources

bioRxiv2025

A new FKBP51-GR-p23-Hsp902 multi-cochaperone complex identified and characterized by site-specific in-cell photocrosslinking

Glucocorticoid receptor (GR) activity and maturation are closely regulated by Hsp90 co-chaperones such as FKBP51, FKBP52 and p23. These co-chaperones bind to and regulate the GR, but their mutual interplay, the details of the interactions between them and their temporal dynamics are still unclear. Here we utilized UV-inducible crosslinking in living cells to map the interaction site of p23 and the GR, as well as p23 and FKBP51 at a single residue resolution. Surprisingly, we detected a novel multi-co-chaperone complex consisting of the GR, p23, FKBP51 and Hsp90, where both FKBP51 and p23 bind to the GR simultaneously. In this complex, FKBP51, but not the close homolog FKBP52, stabilizes the GR-p23 interaction. This is mediated in part by direct contacts between the FK1 domain of FKBP51 and the C-terminus of p23. Our findings refine the state of GR prior to activation, add a new layer of GR regulation by chaperones, provide evidence for the functional differences between FKBP51 and FKBP52, and underscore the power of photocrosslinking to functionally probe protein-protein contacts inside living cells. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=133 SRC="FIGDIR/small/658717v1_ufig1.gif" ALT="Figure 1"> View larger version (38K): org.highwire.dtl.DTLVardef@1431173org.highwire.dtl.DTLVardef@2ebfb9org.highwire.dtl.DTLVardef@12d37e9org.highwire.dtl.DTLVardef@1b1d5e3_HPS_FORMAT_FIGEXP M_FIG C_FIG

biochemistry↗

bioRxiv2023

Large-scale in-cell photocrosslinking at single residue resolution reveals the molecular basis for glucocorticoid receptor regulation by immunophilins

The large immunophilins FKBP51 and FKBP52 play key roles in the Hsp90-mediated maturation of steroid hormone receptors, which is crucial for stress-related disorders and correct sexual embryonic development, respectively 1-3. A prominent regulatory target is the glucocorticoid receptor (GR), whose activation is repressed by FKBP51 4,5 and facilitated by FKBP52 6,7. Despite their vital roles, the molecular modes of action of FKBP51 and FKBP52 are poorly understood since the transient key states of FKBP-mediated GR-regulation have remained experimentally elusive. Here we present the architecture and functional annotation of FKBP51-, FKBP52- and p23-containing Hsp90-apoGR preactivation complexes, trapped by systematic incorporation of photoreactive amino acids 8,9 inside human cells. The identified crosslinking sites depended on a functional Hsp90 chaperone cycle, were disrupted by GR activation, and clustered in characteristic patterns, defining the relative orientation and contact surfaces within the FKBP/p23-apoGR complexes. Strikingly, GR binding to the FKBPFK1 but not the FKBPFK2 domains were modulated by FKBP ligands, explaining the lack of FKBP51-mediated GR derepression by certain classes of FKBP ligands. These findings show how FKBP51 and FKBP52 differentially interact with the apoGR ligand binding domain, they explain the differentiated pharmacology of FKBP51 ligands, and provide a structural basis for the development of FKBP ligands with higher efficacy.

biochemistry↗