Biology subjects

Galvan, A. M.

Publications and source records attributed to Galvan, A. M..

2 recordsLinked to original sources

bioRxiv2018

PARP10 promotes cellular proliferation and tumorigenesis by alleviating replication stress

During carcinogenesis, cells are exposed to increased replication stress due to replication fork arrest at sites of DNA lesions and other difficult to replicate regions. Efficient fork restart and DNA repair are important for cancer cell proliferation. We previously showed that the ADP-ribosyltransferase PARP10 interacts with the replication protein PCNA and promotes lesion bypass by recruiting specialized, non-replicative DNA polymerases. Here, we show that PARP10 is overexpressed in a large proportion of human tumors. To understand the role of PARP10 in cellular transformation, we inactivated PARP10 in HeLa cancer cells by CRISPR/Cas9-mediated gene knockout, and overexpressed it in non-transformed RPE-1 cells. We found that PARP10 promotes cellular proliferation and replication fork elongation. Mechanistically, PARP10 overexpression alleviated cellular sensitivity to replication stress by fostering the restart of stalled replication forks. Importantly, mouse xenograft studies indicated that loss of PARP10 reduces the tumorigenesis activity of HeLa cells, while its overexpression results in tumor formation by non-transformed RPE-1 cells. Our findings indicate that PARP10 promotes cellular transformation by alleviating replication stress, and suggest that targeting PARP10 may represent a novel therapeutic approach.

cancer biology↗

bioRxiv2018

Cell-associated, Heparin-like Molecules Modulate the Ability of LDL to Regulate PCSK9 Uptake

Proprotein convertase subtilisin/kexin type 9 (PCSK9) targets the LDL receptor (LDLR) for degradation, increasing plasma LDL and, consequently, cardiovascular risk. Uptake of secreted PCSK9 is required for its predominant effect on the LDLR. LDL itself inhibits this uptake, though the mechanism by which it does so remains unclear. In this study, we investigated the relationship between LDL, the PCSK9:LDLR interaction, and PCSK9 uptake. We show that LDL inhibits binding of PCSK9 to the epidermal growth factor precursor homology domain A (EGF-A) domain of the LDLR in vitro more impressively than it inhibits PCSK9 uptake in cells. Furthermore, a cell-based factor responsive to heparin-targeting treatments can explain this difference, consistent with its identity as a cell surface heparan sulfate proteoglycan (HSPG), a known co-receptor for PCSK9. Furthermore, we show that the entire PCSK9 prodomain, but not truncated variants, rescues PCSK9 uptake in the presence of LDL, suggesting that PCSK9:LDL binding requires the entire prodomain. Additionally, we show that the gain-of-function (GOF) PCSK9 variant S127R has increased affinity for heparin-like molecules such as HSPGs, potentially explaining the biochemical basis for its phenotype. Overall, our findings suggest a model where PCSK9, LDL, and HSPGs all interact to regulate PCSK9 uptake into the hepatocyte.

biochemistry↗