Publications by authors named "Ya-Ching Fang"

5 Publications

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Identification of MKRN1 as a second E3 ligase for Eag1 potassium channels reveals regulation via differential degradation.

J Biol Chem 2021 Feb 26:100484. Epub 2021 Feb 26.

Institute of Anatomy and Cell Biology, School of Medicine, National Yang-Ming University, Taipei, Taiwan; Brain Research Center, National Yang-Ming University, Taipei, Taiwan. Electronic address:

Mutations in the human gene encoding the neuron-specific Eag1 voltage-gated K channel are associated with neurodevelopmental diseases, indicating an important role of Eag1 during brain development. A disease-causing Eag1 mutation is linked to decreased protein stability that involves enhanced protein degradation by the E3 ubiquitin ligase cullin 7 (CUL7). The general mechanisms governing protein homeostasis of plasma membrane- and endoplasmic reticulum (ER)-localized Eag1 K channels, however, remains unclear. By using yeast two-hybrid screening, we identified another E3 ubiquitin ligase, makorin ring finger protein 1 (MKRN1), as a novel binding partner primarily interacting with the carboxyl-terminal region of Eag1. MKRN1 mainly interacts with ER-localized immature core-glycosylated, as well as nascent non-glycosylated, Eag1 proteins. MKRN1 promotes polyubiquitination and ER-associated proteasomal degradation of immature Eag1 proteins. Although both CUL7 and MKRN1 contribute to ER quality control of immature core-glycosylated Eag1 proteins, MKRN1, but not CUL7, associates with and promotes degradation of nascent, non-glycosylated Eag1 proteins at the ER. In direct contrast to the role of CUL7 in regulating both ER and peripheral quality controls of Eag1, MKRN1 is exclusively responsible for the early stage of Eag1 maturation at the ER. We further demonstrated that both CUL7 and MKRN1 contribute to protein quality control of additional disease-causing Eag1 mutants associated with defective protein homeostasis. Our data suggest that the presence of this dual ubiquitination system differentially maintains Eag1 protein homeostasis and may ensure efficient removal of disease-associated misfolded Eag1 mutant channels.
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http://dx.doi.org/10.1016/j.jbc.2021.100484DOI Listing
February 2021

[Applying Team Resource Management to Accelerate Rewarming Among Patients Undergoing General Anesthesia].

Hu Li Za Zhi 2017 Jun;64(3):82-89

Department of Nursing, Chia- Yi Christian Hospital, and Doctoral Student, Institute of Allied Health Sciences, National Cheng Kung University, Taiwan, ROC.

Background & Problems : Hypothermia is the cause of multiple problems such as delayed awaking from anesthesia, feelings of discomfort, increased oxygen consumption, and increased risks of surgical wound infection and complications. A review of the record of post-operative patients receiving general anesthesia (GA) revealed that only 74% of the patients in our post-anesthesia room (PAR) had restored their body temperature to 36℃ after 60 minutes. Through situation analysis, several causes were identified, including insufficient warming facilities, lack of standard procedures and an audit system, lack of knowledge regarding hyperthermia among nurses, and the incompleteness of perioperative warming interventions performed by the healthcare team.

Purpose: The aim of the present project was to apply team resource management (TRM) to raise the rate of body temperature restoration to 36°C after 60 minutes in our post-anesthesia room (PAR) from 74% to 100%.

Resolution: Several strategies were implemented to accelerate the post-operative rewarming for patients receiving GA, including: establishment of standard operating procedures for warming, conducting routine audits, purchasing warming facilities, conducting in-service education, applying TRM, and cooperating with nurses in operating rooms on executing the warming plan.

Result: After implementing these strategies, our PAR achieved a 100% success rate in raising the body temperature of postoperative patients to 36°C after 60 minutes.

Conclusions: The result demonstrates that hypothermia may be effectively avoided and that the quality of post-operative care may be effectively improved through transdisciplinary teamwork.
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http://dx.doi.org/10.6224/JN.000043DOI Listing
June 2017

Ubiquitin Ligase RNF138 Promotes Episodic Ataxia Type 2-Associated Aberrant Degradation of Human Ca2.1 (P/Q-Type) Calcium Channels.

J Neurosci 2017 03 6;37(9):2485-2503. Epub 2017 Feb 6.

Department of Physiology and

Voltage-gated Ca2.1 channels comprise a pore-forming α subunit with auxiliary αδ and β subunits. Ca2.1 channels play an essential role in regulating synaptic signaling. Mutations in the human gene encoding the Ca2.1 subunit are associated with the cerebellar disease episodic ataxia type 2 (EA2). Several EA2-causing mutants exhibit impaired protein stability and exert dominant-negative suppression of Ca2.1 wild-type (WT) protein expression via aberrant proteasomal degradation. Here, we set out to delineate the protein degradation mechanism of human Ca2.1 subunit by identifying RNF138, an E3 ubiquitin ligase, as a novel Ca2.1-binding partner. In neurons, RNF138 and Ca2.1 coexist in the same protein complex and display notable subcellular colocalization at presynaptic and postsynaptic regions. Overexpression of RNF138 promotes polyubiquitination and accelerates protein turnover of Ca2.1. Disrupting endogenous RNF138 function with a mutant (RNF138-H36E) or shRNA infection significantly upregulates the Ca2.1 protein level and enhances Ca2.1 protein stability. Disrupting endogenous RNF138 function also effectively rescues the defective protein expression of EA2 mutants, as well as fully reversing EA2 mutant-induced excessive proteasomal degradation of Ca2.1 WT subunits. RNF138-H36E coexpression only partially restores the dominant-negative effect of EA2 mutants on Ca2.1 WT functional expression, which can be attributed to defective membrane trafficking of Ca2.1 WT in the presence of EA2 mutants. We propose that RNF138 plays a critical role in the homeostatic regulation of Ca2.1 protein level and functional expression and that RNF138 serves as the primary E3 ubiquitin ligase promoting EA2-associated aberrant degradation of human Ca2.1 subunits. Loss-of-function mutations in the human Ca2.1 subunit are linked to episodic ataxia type 2 (EA2), a dominantly inherited disease characterized by paroxysmal attacks of ataxia and nystagmus. EA2-causing mutants may exert dominant-negative effects on the Ca2.1 wild-type subunit via aberrant proteasomal degradation. The molecular nature of the Ca2.1 ubiquitin-proteasome degradation pathway is currently unknown. The present study reports the first identification of an E3 ubiquitin ligase for Ca2.1, RNF138. Ca2.1 protein stability is dynamically regulated by RNF138 and auxiliary αδ and β subunits. We provide a proof of concept that protecting the human Ca2.1 subunit from excessive proteasomal degradation with specific interruption of endogenous RNF138 function may partially contribute to the future development of a novel therapeutic strategy for EA2 patients.
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http://dx.doi.org/10.1523/JNEUROSCI.3070-16.2017DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6596842PMC
March 2017

Cullin 7 mediates proteasomal and lysosomal degradations of rat Eag1 potassium channels.

Sci Rep 2017 01 18;7:40825. Epub 2017 Jan 18.

Institute of Anatomy and Cell Biology, School of Medicine, National  Yang-Ming University, Taipei, Taiwan.

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.
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http://dx.doi.org/10.1038/srep40825DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5241692PMC
January 2017

Effect of genistein supplementation on tissue genistein and lipid peroxidation of serum, liver and low-density lipoprotein in hamsters.

J Nutr Biochem 2004 Mar;15(3):142-8

Department of Nutrition and Food Sciences, Fu Jen University, Hsinchuang, Taipei 24205, Taiwan.

The aim of this study was to investigate the effects of genistein supplementation in a vitamin E-deficient diet on the genistein concentrations and the lipid oxidation of serum, liver and low-density lipoprotein (LDL) of hamsters. Thirty-six male hamsters were randomly divided into three groups and fed a vitamin E-deficient semisynthetic diet (AIN-76) containing different levels of genistein, i.e., G0 (control group, genistein-free diet), G50 (50 mg genistein/kg diet) and G200 (200 mg genistein/kg diet) for 5 weeks. The concentrations of genistein in serum and liver significantly increased with the increase of genistein supplementation. The vitamin E contents in LDL were higher in hamsters fed G50 or G200 diets than in hamsters fed genistein-free diet. Genistein supplementation to hamsters significantly reduced the propagation rate during conjugated diene formation of LDL oxidation, and the lag time of LDL oxidation in hamsters fed G200 diets was significantly lower than that of G0 diets. In addition, genistein supplementation significantly raised serum total antioxidant capacity and decreased the thiobarbituric acid-reactive substances (TBARS) of LDL and liver in hamsters. However, no significant differences in TBARS were found in serum, irrespective of genistein addition. On the other hand, the relative contents of polyunsaturated fatty acids in LDL were decreased after genistein supplementation. There was a negative correlation between lag time and P/S ratio, and a positive correlation between lag time and vitamin E contents. These data demonstrate that genistein supplementation markedly increased its concentrations in body tissues and reduced oxidative stress of lipid oxidation of serum, liver and LDL.
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http://dx.doi.org/10.1016/j.jnutbio.2003.06.001DOI Listing
March 2004