PCSK9 regulates the NODAL signaling pathway and cellular proliferation in hiPSCs

Proprotein convertase subtilisin kexin type 9 (PCSK9) is a key regulator of low-density lipoprotein (LDL) cholesterol metabolism and the target of lipid-lowering drugs. PCSK9 is mainly expressed in hepatocytes. Here, we show that PCSK9 is highly expressed in undifferentiated human induced pluripotent stem cells (hiPSCs). PCSK9 inhibition in hiPSCs with the use of short hairpin RNA (shRNA), CRISPR/cas9-mediated knockout, or endogenous PCSK9 loss-of-function mutation R104C/V114A unveiled its new role as a potential cell cycle regulator through the NODAL signaling pathway. In fact, PCSK9 inhibition leads to a decrease of SMAD2 phosphorylation and hiPSCs proliferation. Conversely, PCSK9 overexpression stimulates hiPSCs proliferation. PCSK9 can interfere with the NODAL pathway by regulating the expression of its endogenous inhibitor DACT2, which is involved in transforming growth factor (TGF) beta-R1 lysosomal degradation. Using different PCSK9 constructs, we show that PCSK9 interacts with DACT2 through its Cys-His-rich domain (CHRD) domain. Altogether these data highlight a new role of PCSK9 in cellular proliferation and development.

Automated summary

PCSK9, a key regulator of LDL cholesterol metabolism, is found to be highly expressed in undifferentiated hiPSCs. Inhibition of PCSK9 in hiPSCs leads to decreased phosphorylation of SMAD2 and cell proliferation, while overexpression of PCSK9 stimulates cell proliferation by regulating the expression of DACT2, an endogenous inhibitor involved in TGF beta-R1 lysosomal degradation. This highlights a new role of PCSK9 in cellular proliferation and development.