Chutikarn Butkinaree1, Liang Guo, Bhama Ramkhelawon, Amarylis Wanschel, Jeffrey L Brodsky, Kathryn J Moore, Edward A Fisher. 1. From the Department of Medicine, Leon H. Charney Division of Cardiology, Department of Cell Biology, and the Marc and Ruti Bell Vascular Biology and Disease Program, New York University School of Medicine (C.B., L.G., B.R., A.W., K.J.M., E.A.F.); and Department of Biological Sciences, University of Pittsburgh, PA (J.L.B.). C.B. is currently affiliated with Laboratory of Biochemical Neuroendocrinology, Clinical Research Institute of Montreal, Montreal, Quebec, Canada.
Abstract
OBJECTIVE: One of the major risk factors for atherosclerosis is the plasma level of low-density lipoprotein (LDL), which is a product of very-low-density lipoprotein (VLDL). Hepatic apolipoprotein B100 (apoB100) is the essential component that provides structural stability to VLDL particles. Newly translated apoB100 is partially lipidated in the endoplasmic reticulum (ER), forming nascent apoB100-VLDL particles. These particles are further modified to form fully mature VLDLs in the Golgi apparatus. Therefore, the transport of nascent VLDL from the ER to the Golgi represents a critical step during VLDL maturation and secretion and in regulating serum LDL cholesterol levels. Our previous studies showed that apoB100 exits the ER in coat complex II vesicles (COPII), but the cohort of related factors that control trafficking is poorly defined. APPROACH AND RESULTS: Expression levels of Kelch-like protein 12 (KLHL12), an adaptor protein known to assist COPII-dependent transport of procollagen, were manipulated by using a KLHL12-specific small interfering RNA and a KLHL12 expression plasmid in the rat hepatoma cell line, McArdle RH7777. KLHL12 knockdown decreased the secreted and intracellular pools of apoB100, an effect that was attenuated in the presence of an autophagy inhibitor. KLHL12 knockdown also significantly reduced secretion of the most lipidated apoB100-VLDL species and led to the accumulation of apoB100 in the ER. Consistent with these data, KLHL12 overexpression increased apoB100 recovery and apoB100-VLDL secretion. Images obtained from confocal microscopy revealed colocalization of apoB100 and KLHL12, further supporting a direct link between KLHL12 function and VLDL trafficking from the ER. CONCLUSIONS: KLHL12 plays a critical role in facilitating the ER exit and secretion of apoB100-VLDL particles, suggesting that KLHL12 modulation would influence plasma lipid levels.
OBJECTIVE: One of the major risk factors for atherosclerosis is the plasma level of low-density lipoprotein (LDL), which is a product of very-low-density lipoprotein (VLDL). Hepatic apolipoprotein B100 (apoB100) is the essential component that provides structural stability to VLDL particles. Newly translated apoB100 is partially lipidated in the endoplasmic reticulum (ER), forming nascent apoB100-VLDL particles. These particles are further modified to form fully mature VLDLs in the Golgi apparatus. Therefore, the transport of nascent VLDL from the ER to the Golgi represents a critical step during VLDL maturation and secretion and in regulating serum LDL cholesterol levels. Our previous studies showed that apoB100 exits the ER in coat complex II vesicles (COPII), but the cohort of related factors that control trafficking is poorly defined. APPROACH AND RESULTS: Expression levels of Kelch-like protein 12 (KLHL12), an adaptor protein known to assist COPII-dependent transport of procollagen, were manipulated by using a KLHL12-specific small interfering RNA and a KLHL12 expression plasmid in the rathepatoma cell line, McArdle RH7777. KLHL12 knockdown decreased the secreted and intracellular pools of apoB100, an effect that was attenuated in the presence of an autophagy inhibitor. KLHL12 knockdown also significantly reduced secretion of the most lipidated apoB100-VLDL species and led to the accumulation of apoB100 in the ER. Consistent with these data, KLHL12 overexpression increased apoB100 recovery and apoB100-VLDL secretion. Images obtained from confocal microscopy revealed colocalization of apoB100 and KLHL12, further supporting a direct link between KLHL12 function and VLDL trafficking from the ER. CONCLUSIONS:KLHL12 plays a critical role in facilitating the ER exit and secretion of apoB100-VLDL particles, suggesting that KLHL12 modulation would influence plasma lipid levels.
Authors: O Kuge; C Dascher; L Orci; T Rowe; M Amherdt; H Plutner; M Ravazzola; G Tanigawa; J E Rothman; W E Balch Journal: J Cell Biol Date: 1994-04 Impact factor: 10.539
Authors: Nicole Ehrhardt; Michael E Doche; Shuang Chen; Hui Z Mao; Meghan T Walsh; Candy Bedoya; Maha Guindi; Weidong Xiong; Joseph Ignatius Irudayam; Jahangir Iqbal; Sebastien Fuchs; Samuel W French; M Mahmood Hussain; Moshe Arditi; Vaithilingaraja Arumugaswami; Miklós Péterfy Journal: Hum Mol Genet Date: 2017-07-15 Impact factor: 5.121