title: Interactome network analysis identifies multiple caspase-6 interactors involved in the pathogenesis of HD.
abstract: Caspase-6 (CASP6) has emerged as an important player in Huntington disease (HD), Alzheimer disease (AD) and cerebral ischemia, where it is activated early in the disease process. CASP6 also plays a key role in axonal degeneration, further underscoring the importance of this protease in neurodegenerative pathways. As a protein's function is modulated by its protein-protein interactions, we performed a high-throughput yeast-2-hybrid (Y2H) screen against ∼17,000 human proteins to gain further insight into the function of CASP6. We identified a high-confidence list of 87 potential CASP6 interactors. From this list, 61% are predicted to contain a CASP6 recognition site. Of nine candidate substrates assessed, six are cleaved by CASP6. Proteins that did not contain a predicted CASP6 recognition site were assessed using a LUMIER assay approach, and 51% were further validated as interactors by this method. Of note, 54% of the high-confidence interactors identified show alterations in human HD brain at the mRNA level, and there is a significant enrichment for previously validated huntingtin (HTT) interactors. One protein of interest, STK3, a pro-apoptotic kinase, was validated biochemically to be a CASP6 substrate. Furthermore, our results demonstrate that in striatal cells expressing mutant huntingtin (mHTT), an increase in full length and fragment levels of STK3 are observed. We further show that caspase-3 is not essential for the endogenous cleavage of STK3. Characterization of the interaction network provides important new information regarding key pathways of interactors of CASP6 and highlights potential novel therapeutic targets for HD, AD and cerebral ischemia.
authors.affiliation: Max Delbrück Centrum für Molekulare Medizin Berlin-Buch, Berlin 13125, Germany.
authors.forename: Sean-Patrick
authors.initials: SP
authors.lastname: Riechers
authors.affiliation: Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute, Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada V5Z 4H4.
authors.forename: Stefanie
authors.initials: S
authors.lastname: Butland
authors.affiliation: Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute, Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada V5Z 4H4.
authors.forename: Yu
authors.initials: Y
authors.lastname: Deng
authors.affiliation: Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute, Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada V5Z 4H4.
authors.forename: Niels
authors.initials: N
authors.lastname: Skotte
authors.affiliation: Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute, Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada V5Z 4H4.
authors.forename: Dagmar E
authors.initials: DE
authors.lastname: Ehrnhoefer
authors.affiliation: Max Delbrück Centrum für Molekulare Medizin Berlin-Buch, Berlin 13125, Germany.
authors.forename: Jenny
authors.initials: J
authors.lastname: Russ
authors.affiliation: Department of Pharmacology and Physiology and.
authors.forename: Jean
authors.initials: J
authors.lastname: Laine
authors.affiliation: Department of Pharmacology and Physiology and, Research Center on Aging, University of Sherbrooke, Sherbrooke, Quebec, Canada J1H 5N4.
authors.forename: Melissa
authors.initials: M
authors.lastname: Laroche
authors.affiliation: Translational Laboratory in Genetic Medicine, Agency for Science, Technology and Research and Department of Medicine, National University of Singapore, 117609 Singapore, Singapore.
authors.forename: Mahmoud A
authors.initials: MA
authors.lastname: Pouladi
authors.affiliation: Max Delbrück Centrum für Molekulare Medizin Berlin-Buch, Berlin 13125, Germany.
authors.forename: Erich E
authors.initials: EE
authors.lastname: Wanker
authors.affiliation: Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute, Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada V5Z 4H4.
authors.forename: Michael R
authors.initials: MR
authors.lastname: Hayden
authors.affiliation: Department of Pharmacology and Physiology and, Research Center on Aging, University of Sherbrooke, Sherbrooke, Quebec, Canada J1H 5N4, rona.graham@usherbrooke.ca.
authors.forename: Rona K
authors.initials: RK
authors.lastname: Graham
mesh_terms: D001665:Binding Sites; D053178:Caspase 6 / Q000378:metabolism*; D002460:Cell Line; D005786:Gene Expression Regulation; D006801:Humans; D000071058:Huntingtin Protein / Q000235:genetics; D006816:Huntington Disease / Q000378:metabolism* / Q000473:pathology*; D008954:Models, Biological; D060066:Protein Interaction Maps; D011499:Protein Processing, Post-Translational; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D000090742:Serine-Threonine Kinase 3; D020798:Two-Hybrid System Techniques; D000099317:Hippo Kinases
chemical_list: D053178:Caspase 6; D000071058:Huntingtin Protein; D017346:Protein Serine-Threonine Kinases; D000090742:Serine-Threonine Kinase 3; C086055:HTT protein, human; C097835:STK3 protein, human; D000099317:Hippo Kinases; C505514:CASP6 protein, human