9dry
From Proteopedia
CHIP U-box dimer bound to Fab 2F1
Structural highlights
DiseaseCHIP_HUMAN Cerebellar ataxia - hypogonadism. The disease is caused by mutations affecting the gene represented in this entry. FunctionCHIP_HUMAN E3 ubiquitin-protein ligase which targets misfolded chaperone substrates towards proteasomal degradation. Collaborates with ATXN3 in the degradation of misfolded chaperone substrates: ATXN3 restricting the length of ubiquitin chain attached to STUB1/CHIP substrates and preventing further chain extension. Ubiquitinates NOS1 in concert with Hsp70 and Hsp40. Modulates the activity of several chaperone complexes, including Hsp70, Hsc70 and Hsp90. Mediates transfer of non-canonical short ubiquitin chains to HSPA8 that have no effect on HSPA8 degradation. Mediates polyubiquitination of DNA polymerase beta (POLB) at 'Lys-41', 'Lys-61' and 'Lys-81', thereby playing a role in base-excision repair: catalyzes polyubiquitination by amplifying the HUWE1/ARF-BP1-dependent monoubiquitination and leading to POLB-degradation by the proteasome. Mediates polyubiquitination of CYP3A4. Ubiquitinates EPHA2 and may regulate the receptor stability and activity through proteasomal degradation.[1] [2] [3] [4] [5] [6] [7] [8] Publication Abstract from PubMedCarboxyl-terminus of Hsp70-Interacting Protein (CHIP) is an E3 ubiquitin ligase that marks misfolded substrates for degradation. Hyper-activation of CHIP has been implicated in multiple diseases, including cystic fibrosis and cancer, suggesting that it may be a potential drug target. However, there are few tools available for exploring this possibility. Moreover, the best ways of inhibiting CHIP's function are not obvious, as this complex protein is composed of a tetratricopeptide repeat (TPR) domain, a U-box domain, and a coiled-coil domain that mediates homodimerization. To probe the structure and function of CHIP, we report an antibody panning campaign that yielded six recombinant Fabs with affinity for CHIP. Interestingly, these antibodies varied in their binding site(s) and impact on CHIP function, such as inhibiting TPR interactions, autoubiquitination, and/or substrate ubiquitination. Of particular interest, antibody 2F1 nearly eliminated substrate binding (IC(50) = 2.7 muM) and limited ubiquitination and autoubiquitination. Cryo-electron microscopy of the 2F1:CHIP complex revealed a 2:1 binding mode (Fab:CHIP dimer), with 2F1 bound to the U-box domain and simultaneously displacing the TPR domain. Together, these studies provide insight into ways of inhibiting CHIP's activity and provide a series of new probes for exploring the function of this important E3 ubiquitin ligase. Recombinant antibodies inhibit enzymatic activity of the E3 ubiquitin ligase CHIP via multiple mechanisms.,Chung DH, Connelly EJ, Unnikrishnan A, Chuo SW, Wucherer K, Nadel CM, Gestwicki JE, Southworth DR, Craik CS J Biol Chem. 2025 Jan 23;301(3):108220. doi: 10.1016/j.jbc.2025.108220. PMID:39863102[9] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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