title: Cullin 7 mediates proteasomal and lysosomal degradations of rat Eag1 potassium channels.
abstract: Mammalian Eag1 (Kv10.1) potassium (K+) channels are widely expressed in the brain. Several mutations in the gene encoding human Eag1 K+channel have been associated with congenital neurodevelopmental anomalies. Currently very little is known about the molecules mediating protein synthesis and degradation of Eag1 channels. Herein we aim to ascertain the protein degradation mechanism of rat Eag1 (rEag1). We identified cullin 7 (Cul7), a member of the cullin-based E3 ubiquitin ligase family, as a novel rEag1 binding partner. Immunoprecipitation analyses confirmed the interaction between Cul7 and rEag1 in heterologous cells and neuronal tissues. Cul7 and rEag1 also exhibited significant co-localization at synaptic regions in neurons. Over-expression of Cul7 led to reduced protein level, enhanced ubiquitination, accelerated protein turn-over, and decreased current density of rEag1 channels. We provided further biochemical and morphological evidence suggesting that Cul7 targeted endoplasmic reticulum (ER)- and plasma membrane-localized rEag1 to the proteasome and the lysosome, respectively, for protein degradation. Cul7 also contributed to protein degradation of a disease-associated rEag1 mutant. Together, these results indicate that Cul7 mediates both proteasomal and lysosomal degradations of rEag1. Our findings provide a novel insight to the mechanisms underlying ER and peripheral protein quality controls of Eag1 channels.
authors.affiliation: Institute of Anatomy and Cell Biology, School of Medicine, National  Yang-Ming University, Taipei, Taiwan.|Department of Physiology, College of Medicine, National Taiwan University, Taipei, Taiwan.
authors.forename: Po-Hao
authors.initials: PH
authors.lastname: Hsu
authors.affiliation: Institute of Anatomy and Cell Biology, School of Medicine, National  Yang-Ming University, Taipei, Taiwan.
authors.forename: Yu-Ting
authors.initials: YT
authors.lastname: Ma
authors.affiliation: Institute of Anatomy and Cell Biology, School of Medicine, National  Yang-Ming University, Taipei, Taiwan.|Department of Physiology, College of Medicine, National Taiwan University, Taipei, Taiwan.
authors.forename: Ya-Ching
authors.initials: YC
authors.lastname: Fang
authors.affiliation: Department of Physiology, College of Medicine, National Taiwan University, Taipei, Taiwan.
authors.forename: Jing-Jia
authors.initials: JJ
authors.lastname: Huang
authors.affiliation: Institute of Anatomy and Cell Biology, School of Medicine, National  Yang-Ming University, Taipei, Taiwan.|Brain Research Center, National Yang-Ming University, Taipei, Taiwan.
authors.forename: Yu-Ling
authors.initials: YL
authors.lastname: Gan
authors.affiliation: Institute of Anatomy and Cell Biology, School of Medicine, National  Yang-Ming University, Taipei, Taiwan.
authors.forename: Pei-Tzu
authors.initials: PT
authors.lastname: Chang
authors.affiliation: School of Medicine, Fu-Jen Catholic University, Hsin-Chuang, New Taipei City, Taiwan.
authors.forename: Guey-Mei
authors.initials: GM
authors.lastname: Jow
authors.affiliation: Department of Physiology, College of Medicine, National Taiwan University, Taipei, Taiwan.
authors.forename: Chih-Yung
authors.initials: CY
authors.lastname: Tang
authors.affiliation: Institute of Anatomy and Cell Biology, School of Medicine, National  Yang-Ming University, Taipei, Taiwan.|Brain Research Center, National Yang-Ming University, Taipei, Taiwan.
authors.forename: Chung-Jiuan
authors.initials: CJ
authors.lastname: Jeng
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D044842:Cullin Proteins / Q000235:genetics / Q000378:metabolism*; D003513:Cycloheximide / Q000494:pharmacology; D004721:Endoplasmic Reticulum / Q000378:metabolism; D051638:Ether-A-Go-Go Potassium Channels / Q000235:genetics / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D007976:Leupeptins / Q000494:pharmacology; D008247:Lysosomes / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D055550:Protein Stability / Q000187:drug effects; D059748:Proteolysis / Q000187:drug effects; D051381:Rats
chemical_list: D044842:Cullin Proteins; D051638:Ether-A-Go-Go Potassium Channels; C496886:Kcnh1 protein, rat; D007976:Leupeptins; D003513:Cycloheximide; D046988:Proteasome Endopeptidase Complex; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde