Dataset Information

Calpain activity is regulated by a KCTD7–cullin 3 complex via non-degradative ubiquitination

ABSTRACT: Calpains are a class of non-lysosomal cysteine proteases that exert their regulatory functions via limited proteolysis of their substrates. Similar to the lysosomal and proteasomal systems, calpain dysregulation is implicated in the pathogenesis of neurodegenerative disease and cancer. Despite intensive efforts placed on the identification of mechanisms that regulate calpains, however, global regulators of calpains activity have remained elusive. Here we show that calpains are regulated by KCTD7, a cytosolic protein of previously uncharacterized function whose pathogenic mutations result in epilepsy, progressive ataxia, and severe neurocognitive deterioration. We show that KCTD7 works in complex with Cullin-3 and Rbx1 to execute atypical, non-degradative ubiquitination of calpains at specific sites (K398 of calpain 1, and K280 and K674 of calpain 2). Experiments based on single-lysine mutants of ubiquitin determined that KCTD7 mediates ubiquitination of calpain 1 via K6-, K27-, K29-, and K63-linked chains, whereas it uses K6- mediated ubiquitination to modify calpain 2. Loss of KCTD7-mediated ubiquitination of calpains led to calpain hyperactivation, aberrant cleavage of downstream targets, and caspase-3 activation. CRISPR/Cas9-mediated knockout of Kctd7 in mice phenotypically recapitulated human KCTD7 deficiency and resulted in calpain hyperactivation, behavioral impairments, and neurodegeneration. These phenotypes were largely prevented by pharmacological inhibition of calpains, thus demonstrating a major role of calpain dysregulation in KCTD7-associated disease. Finally, we determined that Cullin-3–KCTD7 mediates ubiquitination of all ubiquitous calpains. These results unveil a global mechanism and potential target to restrain calpain activity in human disease and shed light on the molecular pathogenesis of KCTD7-associated disease.

INSTRUMENT(S): Bruker Daltonics timsTOF series

ORGANISM(S): Homo Sapiens (human)

SUBMITTER: Byoung-Kyu Cho

LAB HEAD: Young Ah Goo

PROVIDER: PXD038842 | Pride | 2023-05-10

REPOSITORIES: Pride

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Publications

Calpain activity is negatively regulated by a KCTD7-Cullin-3 complex via non-degradative ubiquitination.

Sharma Jaiprakash J Mulherkar Shalaka S Chen Uan-I UI Xiong Yan Y Bajaj Lakshya L Cho Byoung-Kyu BK Goo Young Ah YA Leung Hon-Chiu Eastwood HE Tolias Kimberley F KF Sardiello Marco M

Cell discovery 20230324 1

Calpains are a class of non-lysosomal cysteine proteases that exert their regulatory functions via limited proteolysis of their substrates. Similar to the lysosomal and proteasomal systems, calpain dysregulation is implicated in the pathogenesis of neurodegenerative disease and cancer. Despite intensive efforts placed on the identification of mechanisms that regulate calpains, however, calpain protein modifications that regulate calpain activity are incompletely understood. Here we show that cal ...[more]

PMID: 36964131

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Project description:Huntington’s disease is caused by a polyglutamine repeat expansion at the N-terminus of the huntingtin protein which affects the function and folding of the protein, and results in intracellular protein aggregates. Here, we examined whether this mutation leads to altered ubiquitination of huntingtin and other proteins in both soluble and insoluble fractions of brain lysates of the Q175 knock-in Huntington disease mouse model and the Q20 wild-type mouse model. Ubiquitination sites are detected by identification of Gly-Gly (diGly) remnant motifs that remain on modified lysine residues after digestion. We identified K6, K9, K132, K804 and K837 as endogenous ubiquitination sites of soluble huntingtin, with wild-type huntingtin being mainly ubiquitinated at K132, K804 and K837. Mutant huntingtin protein levels were strongly reduced in the soluble fraction while K6 and K9 were mainly ubiquitinated. In the insoluble fraction increased levels of huntingtin K6 and K9 diGly sites were observed for mutant huntingtin as compared to wild type. Besides huntingtin, proteins with various roles, including membrane organization, transport, mRNA processing, gene transcription, translation, catabolic processes and oxidative phosphorylation, were differently expressed or ubiquitinated in wild-type and mutant huntingtin brain tissues. Correlating protein and diGly site fold-changes in the soluble fraction revealed that diGly site abundances of the majority of the proteins were not related to protein fold-changes, indicating that these proteins were differentially ubiquitinated in the Q175 mice. In contrast, both the fold-change of the protein level and diGly site level were increased for several proteins in the insoluble fraction, including ubiquitin, ubiquilin-2, sequestosome-1/p62 and myo5a. Our data sheds light on putative novel proteins involved in different cellular processes as well as their ubiquitination status in Huntington’s disease, which forms the basis for further mechanistic studies to understand the role of differential ubiquitination of huntingtin as well as ubiquitin-regulated processes in Huntington’s disease.

Dataset Information

Calpain activity is regulated by a KCTD7–cullin 3 complex via non-degradative ubiquitination

Publications

Calpain activity is negatively regulated by a KCTD7-Cullin-3 complex via non-degradative ubiquitination.

Similar Datasets

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