Biology subjects

Blanchette, P.

Publications and source records attributed to Blanchette, P..

4 recordsLinked to original sources

bioRxiv2026

Viral inhibition of the anaphase promoting complex enhances replication by elevating nucleotide pools

The anaphase promoting complex/cyclosome (APC/C) is a large, ubiquitin ligase and a central regulator of cell cycle progression. By targeting key substrates for degradation during mitosis and G1 phase, the APC/C coordinates metabolic fluctuations that occur during the cell cycle. A diverse range of viruses have convergently evolved mechanisms to bind and inhibit the APC/C; however, a molecular understanding for these interactions has never been demonstrated. Here, we use chicken anemia virus (CAV), a small single-stranded DNA virus encoding only three proteins, to demonstrate the importance of viral APC/C inhibition during replication. We show that the Vp3 protein of CAV inhibits the APC/C, causing a dramatic mitotic arrest during infection. Mutant virus lacking Vp3 are defective for replication and can be rescued by APC/C inhibition. Metabolomic profiling during CAV infection revealed that Vp3 expression mediates a broad increase in nucleotide pools. Moreover, viral inhibition of the APC/C resulted in stabilization of enzymes required for nucleotide biosynthesis. These findings suggest that the APC/C is a general target of many viruses to elevate nucleotide levels and facilitate viral genome replication. Author SummaryViruses dramatically reshape the cells they infect in order to replicate. To do this efficiently, many viruses disrupt the hosts normal control systems, particularly those that regulate cell growth and division. One such system is the anaphase promoting complex/cyclosome (APC/C), a key cellular machine that controls when specific proteins are broken down during the cell cycle. Surprisingly, a wide range of viruses--including adenovirus, HIV, human papillomavirus, herpesvirus, and others--have been shown to interfere with the APC/C. Until now, however, it was unclear why so many unrelated viruses target this same pathway. In our study, we used chicken anemia virus (CAV), one of the smallest known animal viruses, as a simple model to uncover the underlying mechanism. CAV produces just three proteins, one of which--called VP3--strongly inhibits the APC/C. We found that this inhibition increases the availability of nucleotides, the basic building blocks needed to copy viral DNA. By disrupting normal cell cycle control, the virus effectively redirects cellular resources toward its own replication. These findings reveal APC/C inhibition as a common and powerful strategy used by diverse viruses, offering new insight into how viruses exploit host cells and highlighting potential targets for future antiviral therapies.

microbiology↗

bioRxiv2021

Out-of-sight or out-of-site? Forays and detection probabilities in single-season occupancy models

Occupancy models have become popular in wildlife survey analyses because they account for the frequent failure to detect individuals of targeted species. Those individuals sometimes move outside sampling sites, i.e. exhibit temporary emigration. In such cases, occupancy models may become difficult to interpret or even misleading either at the species or the individual level, because they confound presence at the site, availability for detection given presence, and actual detection by the observer. We quantified the probabilities of these three components with spruce grouse (Falcipennis canadensis) in southern Quebec, Canada. We conducted call-response surveys of 24 grouse monitored by radio-telemetry. We defined sites empirically as circular areas of 83 m radius centered on the observer, corresponding to the maximum detection distance obtained. Based on telemetry locations, grouse were present at the site during 42 % of the surveys. Six stationary grouse were present during surveys, but were never detected. Thus, only individuals that moved in the presence of the observer (89 %) were considered available for detection. Individuals available for detection were detected in 51 % of the cases. We simulated detection histories and built single-season occupancy models, based on the empirical relationship between detection probability and the distance measured between observers and grouse. When temporary emigration was ignored, site occupancy was{psi} = 0.89, and the associated probability of detection was p = 0.23. When instances of temporary emigration were dropped, estimates were{psi} = 0.88 and p = 0.41. Using only grouse available for detection, estimates were{psi} = 0.87 and p = 0.42. Disentangling the components of detection probabilities had little impact on occupancy estimates, but showed a major effect of temporary emigration on estimated detection probabilities.

ecology↗

bioRxiv2021

AMPK-dependent phosphorylation is required for transcriptional activation of TFEB/TFE3

Increased autophagy and lysosomal activity promote tumor growth, survival and chemo-resistance. During acute starvation, autophagy is rapidly engaged by AMPK activation and mTORC1 inhibition to maintain energy homeostasis and cell survival. TFEB and TFE3 are master transcriptional regulators of autophagy and lysosomal activity and their cytoplasm/nuclear shuttling is controlled by mTORC1-dependent multisite phosphorylation. However, it is not known whether and how the transcriptional activity of TFEB or TFE3 is regulated. We show that AMPK mediates phosphorylation of TFEB and TFE3 on three serine residues, leading to TFEB/TFE3 transcriptional activity upon nutrient starvation, FLCN depletion and pharmacological manipulation of mTORC1 or AMPK. AMPK loss does not affect TFEB/TFE3 nuclear localization nor protein levels but reduces their transcriptional activity. Collectively, we show that mTORC1 specifically controls TFEB/TFE3 cytosolic retention whereas AMPK is essential for TFEB/TFE3 transcriptional activity. This dual and opposing regulation of TFEB/TFE3 by mTORC1 and AMPK is reminiscent of the regulation of another critical regulator of autophagy, ULK1. Surprisingly, we show that chemoresistance is mediated by AMPK-dependent activation of TFEB, which is abolished by pharmacological inhibition of AMPK or mutation of serine 466/467/469 to alanine residues within TFEB. Altogether, we show that AMPK is a key regulator of TFEB/TFE3 transcriptional activity, and we validate AMPK as a promising target in cancer therapy to evade chemotherapeutic resistance.

cancer biology↗

bioRxiv2018

The transcription factors TFEB and TFE3 link the FLCN-AMPK signaling axis to innate immune response and pathogen resistance

TFEB and TFE3 are transcriptional regulators of the innate immune response, but the mechanisms regulating their activation upon pathogen infection are poorly elucidated. Using C. elegans and mammalian models, we report that the master metabolic modulator 5-AMP-activated protein kinase (AMPK) and its negative regulator Folliculin (FLCN) act upstream of TFEB/TFE3 in the innate immune response, independently of the mTORC1 signaling pathway. In nematodes, loss of FLCN or overexpression of AMPK conferred pathogen resistance via activation of TFEB/TFE3-dependent antimicrobial genes, while ablation of total AMPK activity abolished this phenotype. Similarly, in mammalian cells, loss of FLCN or pharmacological activation of AMPK induced TFEB/TFE3-dependent pro-inflammatory cytokine expression. Importantly, a rapid reduction in cellular ATP levels in murine macrophages was observed upon lipopolysaccharide (LPS) treatment accompanied by an acute AMPK activation and TFEB nuclear localization. These results uncover an ancient, highly conserved and pharmacologically actionable mechanism coupling energy status with innate immunity.

immunology↗