tailieunhanh - Báo cáo khoa học: PCSK9 is phosphorylated by a Golgi casein kinase-like kinase ex vivo and circulates as a phosphoprotein in humans

Proprotein convertase subtilisin⁄kexin 9 (PCSK9) is a secreted glycoprotein that regulates the degradation of the low-density lipoprotein receptor. Sin-gle nucleotide polymorphisms in its gene associate with both hypercholes-terolemia and hypocholesterolemia, and studies have shown a significant reduction in the risk of coronary heart disease for ‘loss-of-function’ PCSK9 carriers. | ễFEBS Journal PCSK9 is phosphorylated by a Golgi casein kinase-like kinase ex vivo and circulates as a phosphoprotein in humans Thilina Dewpura1 z Angela Raymond1 z Josee Hamelin2 Nabil G. Seidah2 Majambu Mbikay1 Michel Chretien1 and Janice Mayne1 1 Chronic Disease Program Ottawa Health Research Institute The Ottawa Hospital Canada 2 Laboratory of BiochemicalNeuroendocrinology ClinicalResearch Institute of Montreal Canada Keywords cholesterol hypercholesterolemia kinase PCSK9 phosphoprotein Correspondence J. Mayne Chronic Disease Program Ottawa Health Research Institute 725 Parkdale Avenue Ottawa Ontario K1Y 4E9 Canada Fax 1 613 761 4355 Tel 1 613 798 5555 ext. 16084 E-mail jmayne@ These authors contributed equally to this article Received 4 March 2008 revised 23 April 2008 accepted 6 May 2008 doi Proprotein convertase subtilisin kexin 9 PCSK9 is a secreted glycoprotein that regulates the degradation of the low-density lipoprotein receptor. Single nucleotide polymorphisms in its gene associate with both hypercholesterolemia and hypocholesterolemia and studies have shown a significant reduction in the risk of coronary heart disease for loss-of-function PCSK9 carriers. Previously we reported that proPCSK9 undergoes autocatalytic processing of its prodomain in the endoplasmic reticulum and that its inhibitory prosegment remains associated with it following secretion. Herein we used a combination of mass spectrometry and radiolabeling to report that PCSK9 is phosphorylated at two sites Ser47 in its propeptide and Ser688 in its C-terminal domain. Site-directed mutagenesis suggested that a Golgi casein kinase-like kinase is responsible for PCSK9 phosphorylation based on the consensus site SXE S p . PCSK9 phosphorylation was cell-type specific and occurs physiologically because human plasma PCSK9 is phosphorylated. Interestingly we show that the naturally occurring loss-of-function variant PCSK9 R46L exhibits significantly decreased