Biology subjects

Wang, X.-D.

Publications and source records attributed to Wang, X.-D..

6 recordsLinked to original sources

bioRxiv2024

Fatty acid desaturation guides cellular decisions between ferroptosis and cellular senescence

When subject to damage or stress, cells develop responses in order to maintain tissue homeostasis. Two such decisions are ferroptosis and cellular senescence, but how cells decide between these outcomes remains unclear. Here we show that senescent cells increase levels of multiple membrane-bound polyunsaturated fatty acids (PUFAs), but a specific PUFA, dihomo-gamma-linolenic acid (DGLA, 20:3{omega}-3) is reduced. Exogenous repletion of DGLA or inhibition of delta-5-desaturase, the enzyme that metabolizes DGLA, instead results in cell death by ferroptosis. Senescent cells had elevated levels of other fezzroptosis sensitizers, including labile iron and expression of lipoxygenases - but also increased Gpx4 levels to prevent ferroptosis. Oral DGLA lowered senescent cell burden in aged mice and improved age-related functional outcomes. Finally, obese humans with lowered DGLA desaturation rates showed lower markers of adipose tissue senescence. Together, our data implicate DGLA and its desaturation as a major driver of decisions between senescence and ferroptosis.

cell biology↗

bioRxiv2022

Induced Degradation of Lineage-specific Oncoproteins Drives the Selective PARP1 Inhibitor Toxicity in Small Cell Lung Cancer

A subset of small cell lung cancer (SCLC) shows clinically relevant response to PARP1 inhibitors (PARPi). However, BRCA1/2 mutations are not commonly found in SCLC, and the underlying mechanism(s) of PARPi sensitivity in SCLC is poorly understood. We performed quantitative proteomic analyses and identified proteomic changes that signify PARPi responses in a large panel of molecularly annotated patient-derived SCLC lines. We found that the toxicity of PARPi in SCLC could be explained, at least in part, by the PARPi-induced degradation of key lineage-specific oncoproteins including ASCL1, NEUROD1, POU2F3, KDM4A, and KDM5B. Importantly, the degradation of these SCLC lineage-specific oncoproteins could also be induced by commonly used chemotherapeutic agents. Biochemical experiments showed that PARPi-induced activation of E3 ligases (e.g., HUWE1 and RNF8) mediated the ubiquitin-proteasome system (UPS)-dependent degradation of these oncoproteins. Interestingly, although PARPi resulted in a general DNA damage response in SCLC cells, this signal is sensed by different SCLC cell lines to generate a cell-specific response. The dissection of the cell-specific oncoprotein degradation response led to the identification of potentially predictive biomarkers for PARPi in SCLC. The combination of PARPi and agents targeting these pathways led to dramatically improved cytotoxicity in SCLC. PARPi-induced degradation of lineage-specific oncoproteins therefore represents a novel mechanism to explain the efficacy of PARPi in tumors without BRCA1/2 mutations. HighlightsO_LIQuantitative mass spectrometric analysis identifies proteomic changes associated with PARPi treatment in a large panel of SCLC cell lines. C_LIO_LIPARPi leads to the degradation of lineage-specific oncoproteins (e.g., ASCL1 and KDM4A) via the DNA damage responsive E3 ubiquitin ligases (e.g., HUWE1 and RNF8). C_LIO_LIA combination of PARPi and agents targeting the lineage-specific oncoproteins offers a more complete and durable therapeutic response in SCLC, compared to PARPi alone. C_LIO_LIExpression of lineage-specific oncoproteins and the associated ubiquitination machinery are predictive biomarkers for PARPi-induced cytotoxicity in SCLC. C_LI

cancer biology↗

bioRxiv2022

Nimbolide Targets RNF114 to Induce the Trapping of PARP1 and Poly-ADP-Ribosylation-Dependent DNA Repair Factors

PARP1 is an abundant nuclear enzyme that is critically involved in DNA damage response. Its main enzymatic function is to catalyze a protein post-translational modification known as poly-ADP-ribosylation (PARylation). Despite the tremendous progresses of PARP1 inhibitors (PARPi) in the clinic, the basic mechanism of action of PARPi is poorly understood. Recent studies point to PARP1 trapping as a key factor driving the cytotoxic and immunomodulatory functions of PARPi. However, the molecular underpinnings of PARP1 trapping remain elusive. Here, using an unbiased, quantitative proteomic screen, we identified RING finger protein 114 (RNF114), as a PARylation-dependent, ubiquitin E3 ligase involved in DNA damage response. Upon sensing DNA damage, RNF114 was recruited, in a PAR-dependent manner, to the DNA lesions, where it specifically targeted PARylated-PARP1 for ubiquitin-proteasomal degradation. The blockade of this pathway interfered with the removal of PARP1 from the DNA damage site, leading to profound PARP1 trapping. We show that a natural product, Nimbolide, targeted RNF114 to block the degradation and removal of PARylated-PARP1 from DNA lesions. Unlike conventional PARPi, nimbolide treatment induced the trapping of both PARP1 and PARylation-dependent DNA repair factors. This unique mechanism of action of nimbolide translated into its superior cytotoxic effects against BRCA-deficient cancers. Furthermore, we demonstrated that, as a super trapper of both PARylated-PARP1 and PARylation-dependent DNA repair factors, nimbolide was able to overcome the intrinsic and acquired resistance to PARPi. Finally, we showed that nimbolide treatment activated innate immune signaling and was able to synergize with various cytotoxic agents. These results point to the exciting possibility of targeting homologous recombination-deficient cancers using nimbolide and its analogs.

cancer biology↗

bioRxiv2021

Pro70 Hydroxylation of Actin Impairs Cell Motility Through Binding with VHL and Blocking His73 Methylation

Actin filaments generate intrinsic forces that are essential for cell motility. This process is tightly regulated by various posttranslational modifications (PTMs), including acetylation, arginylation, and oxidation. However, the role of actin hydroxylation in regulating its dynamics remains poorly understood. Here, we demonstrate that the inhibition of Prolyl Hydroxylase Domain-containing proteins (PHDs) activity significantly promotes actin polymerization and enhances cell motility. Using hydroxylation proteomics, we identified actin as a substrate for PHDs, with hydroxylation occurring at multiple proline residues, especially at proline 70 (Pro70). This modification recruits the von Hippel-Lindau (VHL) tumor suppressor protein, which then leads to the disruption of the interaction between actin and the histidine methyltransferase SET Domain Containing 3 (SETD3). Consequently, SETD3-mediated methylation of histidine 73 (His73) on actin is suppressed, impairing actin polymerization and compromising cell motility. Notably, genetic loss of VHL or pharmacological inhibition of PHDs restores His73 methylation, enhances actin filament formation, and promotes cell motility. Together, our findings uncover a novel regulatory crosstalk between hydroxylation and methylation on actin, establishing a critical mechanism by which PTMs fine-tune actin dynamics to govern cell motility. HighlightsO_LIMK-8617 augments cell motility and actin polymerization in VHL dependent manner; C_LIO_LIHydroxylation proteomics reveals that actin is hydroxylated by PHDs; C_LIO_LIHydroxylation at Pro70 recruits VHL, disrupting actins interaction with SETD3 and reducing His73 methylation; C_LIO_LIGenetic loss of VHL in clear cell renal cell carcinoma (ccRCC) potentially promotes cell motility by increasing His73 methylation on actin. C_LI

biochemistry↗

bioRxiv2021

Quantitative Tyr Phosphoproteomic Analyses Identify Cholesterol as a Master Regulator of Tumor Adaptive Resistance to MAPK Inhibition

Although targeted inhibition of the MAPK pathway has achieved remarkable patient responses in many cancers with MAPK hyperactivation, the development of resistance has remained a critical challenge. Besides genomic resistance mechanisms, adaptive tumor response also underlies the resistance to targeted MAPK inhibitors. It is being increasingly appreciated that such bypass mechanisms often lead to the activation of many pro-survival kinases, which complicates the rational design of combination therapies. Here we performed global tyrosine phosphoproteomic (pTyr) analyses and demonstrated that targeted inhibition of MAPK signaling in melanoma cells leads to a profound remodeling of the pTyr proteome. Intriguingly, many of these kinases contain a cholesterol binding motif, suggesting that altered cholesterol metabolism might drive, in a coordinated fashion, the activation of these kinases. Indeed, we found a dramatic accumulation of intracellular cholesterol in melanoma cells (with BRAFV600E mutations) and non-small cell lung cancer cells (with KRASG12C mutations) treated with MAPK and KRASG12C inhibitors, respectively. Importantly, depletion of cholesterol not only prevented the MAPK inhibition-induced feedback activation of pTyr singling but also enhanced the cytotoxic effects of MAPK inhibitors, both in vitro and in vivo. Taken together, our findings provide the evidence suggesting that cholesterol functions as a master regulator of the tumor adaptive response to targeted MAPK inhibitors. These results also suggest that MAPK inhibitors could be combined with cholesterol-lowering agents to achieve a more complete and durable response in tumors with hyperactive MAPK signaling.

cell biology↗

bioRxiv2018

LARP1 is a major phosphorylation substrate of mTORC1

The mammalian target of rapamycin complex 1 (mTORC1) controls critical cellular functions such as protein synthesis, lipid metabolism, protein turnover and ribosome biogenesis through the phosphorylation of multiple substrates. In this study, we examined the phosphorylation of a recently identified target of mTORC1: La-related protein 1 (LARP1), a member of the LARP superfamily. Previously, we and others have shown that LARP1 plays an important role in repressing TOP mRNA translation downstream of mTORC1. LARP1 binds the 7-methylguanosine triphosphate (m7Gppp) cap moiety and the adjacent 5terminal oligopyrimidine (5TOP) motif of TOP mRNAs, thus impeding the assembly of the eIF4F complex on these transcripts. mTORC1 plays a critical role in the control of TOP mRNA translation via LARP1 but the precise mechanism by which this occurs is incompletely understood. The data described herein help to elucidate this process. Specifically, it show that: (i) mTORC1 interacts with LARP1, but not other LARP superfamily members, via the C-terminal region that comprises the DM15 domain, (ii) mTORC1 pathway controls the phosphorylation of multiple (up to 26) serine and threonine residues on LARP1 in vivo, (iii) mTORC1 regulates the binding of LARP1 to TOP mRNAs and (iv) phosphorylation of S689 by mTORC1 is particularly important for the association of the DM15 domain of LARP1 with the 5UTR of RPS6 TOP mRNA. These data reveal LARP1 as a major substrate of mTORC1.

biochemistry↗