Novel role of C terminus of Hsc70‐interacting protein (CHIP) ubiquitin ligase on inhibiting cardiac apoptosis and dysfunction
            via
            regulating ERK5‐mediated degradation of inducible cAMP early repressor

The transforming growth factor-β (TGF-β) superfamily of ligands signals along two intracellular pathways, Smad2/3-mediated TGF-β/activin pathway and Smad1/5/8-mediated bone morphogenetic protein pathway. The C terminus of Hsc70-interacting protein (CHIP) serves as an E3 ubiquitin ligase to mediate the degradation of Smad proteins and many other signaling proteins. However, the molecular mechanism for CHIP-mediated down-regulation of TGF-β signaling remains unclear. Here we show that the extreme C-terminal sequence of Smad1 plays an indispensable role in its direct association with the tetratricopeptide repeat (TPR) domain of CHIP. Interestingly, Smad1 undergoes CHIP-mediated polyubiquitination in the absence of molecular chaperones, and phosphorylation of the C-terminal SXS motif of Smad1 enhances the interaction and ubiquitination. We also found that CHIP preferentially binds to Smad1/5 and specifically disrupts the core signaling complex of Smad1/5 and Smad4. We determined the crystal structures of CHIP-TPR in complex with the phosphorylated/pseudophosphorylated Smad1 peptides and with an Hsp70/Hsc70 C-terminal peptide. Structural analyses and subsequent biochemical studies revealed that the distinct CHIP binding affinities of Smad1/5 or Smad2/3 result from the nonconservative hydrophobic residues at R-Smad C termini. Unexpectedly, the C-terminal peptides from Smad1 and Hsp70/Hsc70 bind in the same groove of CHIP-TPR, and heat shock proteins compete with Smad1/5 for CHIP interaction and concomitantly suppress, rather than facilitate, CHIP-mediated Smad ubiquitination. Thus, we conclude that CHIP inhibits the signaling activities of Smad1/5 by recruiting Smad1/5 from the functional R-/Co-Smad complex and further promoting the ubiquitination/degradation of Smad1/5 in a chaperone-independent manner.

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Differential HspBP1 expression accounts for the greater vulnerability of neurons than astrocytes to misfolded proteins

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1710549114 ◽

2017 ◽

Vol 114 (37) ◽

pp. E7803-E7811 ◽

Cited By ~ 17

Author(s):

Ting Zhao ◽

Yan Hong ◽

Peng Yin ◽

Shihua Li ◽

Xiao-Jiang Li

Keyword(s):

Neurodegenerative Diseases ◽

Critical Role ◽

Misfolded Proteins ◽

Inhibitory Protein ◽

Interacting Protein ◽

C Terminus ◽

Differential Vulnerability ◽

Disease Protein ◽

Knockin Mouse

Although it is well known that astrocytes are less vulnerable than neurons in neurodegenerative diseases, the mechanism behind this differential vulnerability is unclear. Here we report that neurons and astrocytes show markedly different activities in C terminus of Hsp70-interacting protein (CHIP), a cochaperone of Hsp70. In astrocytes, CHIP is more actively monoubiquitinated and binds to mutant huntingtin (mHtt), the Huntington’s disease protein, more avidly, facilitating its K48-linked polyubiquitination and degradation. Astrocytes also show the higher level and heat-shock induction of Hsp70 and faster CHIP-mediated degradation of various misfolded proteins than neurons. In contrast to astrocytes, neurons express abundant HspBP1, a CHIP inhibitory protein, resulting in the low activity of CHIP. Silencing HspBP1 expression via CRISPR-Cas9 in neurons ameliorated mHtt aggregation and neuropathology in HD knockin mouse brains. Our findings indicate a critical role of HspBP1 in differential CHIP/Hsp70 activities in neuronal and glial cells and the greater neuronal vulnerability to misfolded proteins in neurodegenerative diseases.

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The Stability of Wild-type and Deletion Mutants of Human C-terminus Hsp70-interacting Protein (CHIP)

Protein and Peptide Letters ◽

10.2174/0929866511320050005 ◽

2013 ◽

Vol 20 (5) ◽

pp. 524-529 ◽

Cited By ~ 2

Author(s):

Isabel C.R. Millan ◽

Ana L.A. Squillace ◽

Lisandra M. Gava ◽

Carlos H.I. Ramos

Keyword(s):

Protein Chip ◽

Deletion Mutants ◽

Wild Type ◽

Interacting Protein ◽

C Terminus ◽

The Stability

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Liver Cytochrome P450 3A Ubiquitinationin Vivoby gp78/Autocrine Motility Factor Receptor and C Terminus of Hsp70-interacting Protein (CHIP) E3 Ubiquitin Ligases

Journal of Biological Chemistry ◽

10.1074/jbc.m110.167189 ◽

2010 ◽

Vol 285 (46) ◽

pp. 35866-35877 ◽

Cited By ~ 23

Author(s):

Sung-Mi Kim ◽

Poulomi Acharya ◽

Juan C. Engel ◽

Maria Almira Correia

Keyword(s):

Cytochrome P450 ◽

Ubiquitin Ligases ◽

Protein Chip ◽

E3 Ubiquitin Ligases ◽

Cytochrome P450 3A ◽

Autocrine Motility Factor ◽

Interacting Protein ◽

Motility Factor ◽

Liver Cytochrome ◽

C Terminus

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A GIPC1-Palmitate Switch Modulates Dopamine Drd3 Receptor Trafficking and Signaling

Molecular and Cellular Biology ◽

10.1128/mcb.00916-15 ◽

2016 ◽

Vol 36 (6) ◽

pp. 1019-1031 ◽

Cited By ~ 8

Author(s):

Margarita Arango-Lievano ◽

Ozge Sensoy ◽

Amélie Borie ◽

Maithé Corbani ◽

Gilles Guillon ◽

...

Keyword(s):

Posttranslational Modifications ◽

Signaling Proteins ◽

Interacting Protein ◽

Mutant Proteins ◽

C Terminus ◽

Biased Signaling ◽

Dopamine D3 ◽

Dynamics Simulations

Palmitoylation is involved in several neuropsychiatric and movement disorders for which a dysfunctional signaling of the dopamine D3 receptor (Drd3) is hypothesized. Computational modeling of Drd3's homologue, Drd2, has shed some light on the putative role of palmitoylation as a reversible switch for dopaminergic receptor signaling. Drd3 is presumed to be palmitoylated, based on sequence homology with Drd2, but the functional attributes afforded by Drd3 palmitoylation have not been studied. Since these receptors are major targets of antipsychotic and anti-Parkinsonian drugs, a better characterization of Drd3 signaling and posttranslational modifications, like palmitoylation, may improve the prospects for drug development. Using molecular dynamics simulations, we evaluatedin silicohow Drd3 palmitoylation could elicit significant remodeling of the C-terminal cytoplasmic domain to expose docking sites for signaling proteins. We tested this modelin celluloby using the interaction of Drd3 with the G-alpha interacting protein (GAIP) C terminus 1 (GIPC1) as a template. From a series of biochemical studies, live imaging, and analyses of mutant proteins, we propose that Drd3 palmitoylation acts as a molecular switch for Drd3-biased signaling via a GIPC1-dependent route, which is likely to affect the mode of action of antipsychotic drugs.

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