Vakili, K. | bioRxiv Science

bioRxiv2021

DNAJB1-PRKACA in HEK293T cells induces LINC00473 overexpression that depends on PKA signaling

Fibrolamellar carcinoma (FLC) is a primary liver cancer that most commonly arises in adolescents and young adults in a background of normal liver tissue and has an poor prognosis due to lack of effective chemotherapeutic agents. The DNAJB1-PRKACA gene fusion (DP) has been reported in the majority of FLC tumors, however its oncogenic mechanisms remain unclear. Given the paucity of cellular models, in particular FLC tumor cell lines, we hypothesized that engineering the DP fusion gene in HEK293T cells would provide insight into the cellular effects of the fusion gene. We used CRISPR/Cas9 to engineer HEK293T clones expressing DP fusion gene (HEK-DP) and performed transcriptomic, proteomic, and mitochondrial studies to characterize this cellular model. Proteomic analysis of DP interacting partners identified mitochondrial proteins as well as proteins in other subcellular compartments. HEK-DP cells demonstrated significantly elevated mitochondrial fission, which suggests a role for DP in altering mitochondrial dynamics. Transcriptomic analysis of HEK-DP cells revealed a significant increase in LINC00473 expression, similar to what has been observed in primary FLC samples. LINC00473 overexpression was reversible with siRNA targeting of PRKACA as well as pharmacologic targeting of PKA and Hsp40 in HEK-DP cells. Therefore, our model suggests that LINC00473 is a candidate marker for DP activity.

cancer biology↗

bioRxiv2021

Targeting tau mitigates mitochondrial fragmentation and oxidative stress in amyotrophic lateral sclerosis

Understanding the mechanisms underlying amyotrophic lateral sclerosis (ALS) is crucial for the development of new therapies. Recent evidence suggest that tau may be involved in ALS pathogenesis. Here, we demonstrated that hyperphosphorylated tau (pTau-S396) is mis-localized to synapses in human post-mortem motor cortex (mCTX) across ALS subtypes. Treatment with ALS synaptoneurosomes (SNs) derived from post-mortem mCTX, enriched in pTau-S396, increased oxidative stress, induced mitochondrial fragmentation, and altered mitochondrial connectivity in vitro. Furthermore, our findings revealed that pTau-S396 interacts with the pro-fission dynamin-related protein (DRP1), and similar to pTau-S396, DRP1 accumulated in ALS SNs across ALS subtypes. Lastly, reducing tau with a specific bifunctional degrader, QC-01-175, prevented ALS SNs-induced mitochondrial fragmentation and oxidative stress in vitro. Collectively, our findings suggest that increases in pTau-S396 may lead to mitochondrial fragmentation and oxidative stress in ALS and decreasing tau may provide a novel strategy to mitigate mitochondrial dysfunction in ALS. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=173 SRC="FIGDIR/small/436505v1_ufig1.gif" ALT="Figure 1"> View larger version (37K): org.highwire.dtl.DTLVardef@1d805baorg.highwire.dtl.DTLVardef@1601f49org.highwire.dtl.DTLVardef@1a62abforg.highwire.dtl.DTLVardef@40699f_HPS_FORMAT_FIGEXP M_FIG C_FIG O_LIpTau-S396 mis-localizes to synapses in ALS. C_LIO_LIALS synaptoneurosomes (SNs), enriched in pTau-S396, increase oxidative stress and induce mitochondrial fragmentation in vitro. C_LIO_LIpTau-S396 interacts with the pro-fission GTPase DRP1 in ALS. C_LIO_LIReducing tau with a specific degrader, QC-01-175, mitigates ALS SNs-induced mitochondrial fragmentation and increases in oxidative stress in vitro. C_LI

neuroscience↗