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Principal Investigator: John S Chorba
Organization: UNIVERSITY OF CALIFORNIA, SAN FRANCISCO
Fiscal Year: 2024
Award: $363,375
Funding agency: National Heart Lung and Blood Institute
PROJECT SUMMARY/ABSTRACT
Serum low-density lipoprotein (LDL) causes atherosclerotic heart disease. As the LDL receptor (LDLR) on the
liver clears LDL from the blood, upregulating hepatic LDLR reduces both LDL and cardiovascular events. The
self-cleaving protease PCSK9 (proprotein convertase subtilisin/kexin type 9) is a validated therapeutic target; it
chaperones the LDLR for lysosomal degradation, downregulating its function. Antibodies against PCSK9 lower
LDL and improve clinical outcomes, but cost and administration requirements illustrate a need for alternatives.
Liver-targeted siRNA also robustly lowers LDL, but unlike the well-tolerated genetic variants, it removes all
PCSK9 from the cell, raising safety concerns. Though the mechanistic basis for PCSK9's effect on the hepatic
LDLR is well understand, its functions outside this canonical pathway are less clear. Therefore, the overall
goal of our proposal is to develop biochemical tools to mechanistically dissect the biology of PCSK9, so as to
1) anticipate the long-term effects of current anti-PCSK9 therapies and 2) develop the proofs-of-principle for
novel PCSK9-targeting strategies. To this end, we have identified three promising lead compounds that
specifically target intracellular PCSK9. These compounds both inhibit PCSK9 self-proteolysis and also
upregulate LDLR expression. In Aim 1, we will chemically optimize these compounds, confirm the mechanistic
basis of their effects, and validate their function on PCSK9 and the LDLR in an in vivo model. This will
establish novel chemical probes which can be used to study the poorly known function of intracellular PCSK9,
as well as serve as the starting point for an alternative small molecule therapeutic to upregulate the LDLR. We
have also found that additional factors, including heparan sulfate proteoglycans (HSPGs), interact with PCSK9
to modulate its trafficking to the lysosome, suggesting that there are additional drug targets in this pathway. In
Aim 2, we will evaluate the contribution of HSPGs as mediators of the PCSK9 endocytic trafficking required for
LDLR downregulation, both in vitro and in the human. These results will elucidate whether heparins, which are
already approved therapies, could be repurposed to inhibit PCSK9 function. In Aim 3, we will identify and
validate as yet unknown regulators of PCSK9 endocytic trafficking via an unbiased, genome-wide CRISPR
interference screen. These results will help mechanistically define how PCSK9 is trafficked to the lysosome,
provide answers to why PCSK9 only affects certain tissues, and offer potential novel therapeutic targets which
would be anticipated to have similar therapeutic windows to PCSK9 itself. Overall, we expect our study to
provide key information on the safety of long-term PCSK9 inhibition, lay the groundwork for novel treatments,
and identify new therapeutic targets against atherosclerosis.
Terms: <Access to Care><Address><Affect><Antibodies><Anticoagulant Agents><Anticoagulant Drugs><Anticoagulants><Atherosclerosis><Atherosclerotic Cardiovascular Disease><Binding><Biological><Biology><Blood Circulation><Blood Serum><Bloodstream><Body Tissues><CRISPR interference><CRISPR-dCas9-mediated repression><CRISPR/dCas9 interference><CRISPR/dCas9-mediated transcriptional inhibition><CRISPRi><Cardiovascular><Cardiovascular Body System><Cardiovascular Organ System><Cardiovascular system><Cell Body><Cell Surface Receptors><Cell surface><Cells><Chaperone><Chemicals><Cholesterol><Chromosome Mapping><Clinic><Clinical><Clustered Regularly Interspaced Short Palindromic Repeats interference><Coronary Disease><Coronary heart disease><Development><Drug Targeting><Drugs><Engineering><Esteroproteases><Event><Exhibits><Foundations><Gene Localization><Gene Mapping><Gene Mapping Genetics><Gene variant><Genetic><Genetic Alteration><Genetic Change><Genetic defect><Goals><HSPG><Health><Health Services Accessibility><Heart Vascular><Heparan Sulfate Proteoglycan><Heparin><Heparinic Acid><Hepatic><Hepatic Cells><Hepatic Parenchymal Cell><Hepatocyte><Human><Human Genetics><Impairment><In Vitro><Insurance Carriers><Insurers><LDL><LDL Lipoproteins><LDL Receptors><Lead><Linkage Mapping><Lipoprotein LDL Receptors><Liver><Liver Cells><Long-Term Effects><Longterm Effects><Low Density Lipoprotein Receptor><Low-Density Lipoproteins><Lysosomes><Mediating><Mediator><Medication><Mission><Modern Man><Molecular><Molecular Chaperones><Molecular Interaction><Mutation><NIH><National Institutes of Health><Oral><Outcome><Pathway interactions><Patients><Pb element><Peptidases><Peptide Hydrolases><Pharmaceutical Preparations><Phenocopy><Phenotype><Physiologic><Physiological><Price><Proprotein Convertases><Protease Gene><Proteases><Protein Cleavage><Proteinases><Proteoheparan Sulfate><Proteolysis><Proteolytic Enzymes><Receptor Down-Regulation><Regulation><Research Design><Resistance><Role><Safety><Serum><Short interfering RNA><Small Interfering RNA><Study Type><Subtilisins><Therapeutic><Tissues><Total Human and Non-Human Gene Mapping><United States National Institutes of Health><Variant><Variation><access to health services><access to services><access to treatment><accessibility to health services><allele variant><allelic variant><analog><atheromatosis><atherosclerotic disease><atherosclerotic heart disease><atherosclerotic vascular disease><availability of services><beta-Lipoproteins><biochemical tools><biochemistry tools><biologic><blood lipoprotein><blood thinner><cardioprotectant><cardioprotection><cardioprotective><care access><circulatory system><clinical efficacy><cofactor><coronary disorder><cost><cost effective><developmental><drug/agent><gain of function><gene manipulation><genetic manipulation><genetic mapping><genetic variant><genetically manipulate><genetically perturb><genome mutation><genome scale><genome-wide><genomewide><genomic variant><health service access><health services availability><heavy metal Pb><heavy metal lead><hepatic body system><hepatic organ system><improved><improved outcome><in vivo><in vivo Model><inhibitor><innovate><innovation><innovative><insight><loss of function><new drug target><new drug treatments><new druggable target><new drugs><new pharmacological therapeutic><new pharmacotherapy target><new therapeutic target><new therapeutics><new therapy><new therapy target><next generation therapeutics><novel><novel drug target><novel drug treatments><novel druggable target><novel drugs><novel pharmaco-therapeutic><novel pharmacological therapeutic><novel pharmacotherapy target><novel therapeutic target><novel therapeutics><novel therapy><novel therapy target><pathway><pricing><public health relevance><receptor downregulation><receptor expression><repressing CRISPR-dCas9 system><resistant><reuptake><scaffold><scaffolding><screening><screenings><service availability><siRNA><small molecule><small molecule therapeutics><social role><study design><therapeutic target><thrombopoiesis inhibitor><tissue tropism><tool><trafficking><treatment access>