The Biology and Clinical Implications of PCSK7

Discovered in 1996, PCSK7 is the seventh of the 9-membered proprotein convertase subtilisin-kexin (PCSK) family. This article reviews the various aspects of the multifaceted biology of PCSK7 and what makes it an exciting new target for metabolic dysfunction-associated steatotic liver disease (MASLD), affecting ∼30% of the population globally, dyslipidemia, cardiovascular disease, and likely cancer/metastasis. We will systematically review and discuss all the available epidemiological data, and structural, cell biology, and in vivo evidence that eventually led to the discovery of PCSK7 as a novel post-translational regulator of apolipoprotein B. Interestingly, PCSK7 is the only convertase, other than PCSK9, that exhibits noncanonical/nonenzymatic functions, which will be amply described in this review. The data so far have suggested that PCSK7 is a potential safe target in MASLD treatment. This was based on human epidemiological data, as well as mouse Pcsk7 knockout and mRNA translation inhibition using hepatocyte-targeted antisense oligonucleotides following a diet-induced MASLD. Additionally, of all the 9 convertases only the gene deletion of Pcsk7 and/or Pcsk9 in mice leads to healthy and fertile animals with no apparent deleterious consequences, suggesting that their pharmacological targeting is likely safe. Accordingly, the synergistic effects of inhibiting both PCSK7 and PCSK9 in a clinical setting may represent a novel therapy for various diseases. We believe that the current surge in oligonucleotide therapy, with many Food and Drug Administration-approved oligonucleotide-based drugs now available in clinics, and the urgent need for novel MASLD therapeutics present an opportune moment for this timely review article.