Background: Severe acute respiratory syndrome (SARS) is caused by a newly discovered coronavirus (SARS-CoV). No effective prophylactic or post-exposure therapy is currently available.

The proprotein convertase PCSK9 gene is the third locus implicated in familial hypercholesterolemia, emphasizing its role in cardiovascular diseases. Loss of function mutations and gene disruption of PCSK9 resulted in a higher clearance of plasma low density lipoprotein cholesterol, likely due to a reduced degradation of the liver low density lipoprotein receptor (LDLR). In this study, we show that two of the closest family members to LDLR are also PCSK9 targets. These include the very low density lipoprotein receptor (VLDLR) and apolipoprotein E receptor 2 (ApoER2) implicated in neuronal development and lipid metabolism. Our results show that wild type PCSK9 and more so its natural gain of function mutant D374Y can efficiently degrade the LDLR, VLDLR, and ApoER2 either following cellular co-expression or re-internalization of secreted human PCSK9. Such PCSK9-induced degradation does not require its catalytic activity. Membrane-bound PCSK9 chimeras enhanced the intracellular targeting of PCSK9 to late endosomes/lysosomes and resulted in a much more efficient degradation of the three receptors. We also demonstrate that the activity of PCSK9 and its binding affinity on VLDLR and ApoER2 does not depend on the presence of LDLR. Finally, in situ hybridization show close localization of PCSK9 mRNA expression to that of VLDLR in mouse postnatal day 1 cerebellum. Thus, this study demonstrates a more general effect of PCSK9 on the degradation of the LDLR family that emphasizes its major role in cholesterol and lipid homeostasis as well as brain development.Familial hypercholesterolemia is mainly characterized by elevated plasma LDL 2 cholesterol that is highly correlated with cardiovascular diseases (1). The main player in regulating the circulating cholesterol is the low density lipoprotein receptor (LDLR), which is expressed mostly in the liver. Recently, natural mutations in the proprotein convertase PCSK9 (2, 3) have been identified and associated with the third locus implicated in familial hypercholesterolemia (4 -6). The major function of PCSK9 seems to be an enhancement of the degradation of the LDLR (7, 8) in acidic subcellular compartments (3), likely endosomes/lysosomes (9, 10). This can occur either via an extracellular endocytotic route (11), or possibly by a direct cellular circuit not involving cell surface endocytosis of the LDLR (12). The gain of function PCSK9 mutations D374Y (13, 14) or D374H (15) have the highest impact on the development of hypercholesterolemia (16), likely through enhanced binding (17) and degradation of the LDLR (18, 19). The major binding site of LDLR to PCSK9 seems to reside within its first epidermal growth factor-like repeat namely EGF-A (20). Finally, it was recently suggested that the PCSK9-induced degradation of the cell surface LDLR does not require its proteolytic activity (21). One of the unanswered questions is the target specificity of PCSK9, and it is not known, nor obvious, whether other members of the LDLR family are also affected by PCSK9. This family consists of str...

SummaryThe 2013–2015 Ebola virus disease (EVD) epidemic is caused by the Makona variant of Ebola virus (EBOV). Early in the epidemic, genome sequencing provided insights into virus evolution and transmission and offered important information for outbreak response. Here, we analyze sequences from 232 patients sampled over 7 months in Sierra Leone, along with 86 previously released genomes from earlier in the epidemic. We confirm sustained human-to-human transmission within Sierra Leone and find no evidence for import or export of EBOV across national borders after its initial introduction. Using high-depth replicate sequencing, we observe both host-to-host transmission and recurrent emergence of intrahost genetic variants. We trace the increasing impact of purifying selection in suppressing the accumulation of nonsynonymous mutations over time. Finally, we note changes in the mucin-like domain of EBOV glycoprotein that merit further investigation. These findings clarify the movement of EBOV within the region and describe viral evolution during prolonged human-to-human transmission.