TGF-ß1/SMAD3-driven GLI2 isoform expression contributes to aggressive phenotypes of hepatocellular carcinoma.

Hedgehog signaling is activated in response to liver injury, and modulates organogenesis. However, the role of non-canonical hedgehog activation via TGF-ß1/SMAD3 in hepatic carcinogenesis is poorly understood. TGF-ß1/SMAD3-mediated non-canonical activation was found in approximately half of GLI2-positive hepatocellular carcinoma (HCC), and two new GLI2 isoforms with transactivating activity were identified. Phospho-SMAD3 interacted with active GLI2 isoforms to transactivate downstream genes in modulation of stemness, epithelial-mesenchymal transition, chemo-resistance and metastasis in poorly-differentiated hepatoma cells. Non-canonical activation of hedgehog signaling was confirmed in a transgenic HBV-associated HCC mouse model. Inhibition of TGF-ß/SMAD3 signaling reduced lung metastasis in a mouse in situ hepatic xenograft model. In another cohort of 55 HCC patients, subjects with high GLI2 expression had a shorter disease-free survival than those with low expression. Moreover, co-positivity of GLI2 with SMAD3 was observed in 87.5% of relapsed HCC patients with high GLI2 expression, indicating an increased risk of post-resection recurrence of HCC. The findings underscore that suppressing the non-canonical hedgehog signaling pathway may confer a potential strategy in the treatment of HCC.

Rhythmic cilia changes support SCN neuron coherence in circadian clock.

The suprachiasmatic nucleus (SCN) drives circadian clock coherence through intercellular coupling, which is resistant to environmental perturbations. We report that primary cilia are required for intercellular coupling among SCN neurons to maintain the robustness of the internal clock in mice. Cilia in neuromedin S-producing (NMS) neurons exhibit pronounced circadian rhythmicity in abundance and length. Genetic ablation of ciliogenesis in NMS neurons enabled a rapid phase shift of the internal clock under jet-lag conditions. The circadian rhythms of individual neurons in cilia-deficient SCN slices lost their coherence after external perturbations. Rhythmic cilia changes drive oscillations of Sonic Hedgehog (Shh) signaling and clock gene expression. Inactivation of Shh signaling in NMS neurons phenocopied the effects of cilia ablation. Thus, cilia-Shh signaling in the SCN aids intercellular coupling.

Tripartite motif containing 69 elicits ERK2-dependent EYA4 turnover to impart pancreatic tumorigenesis.

Eyes absent homologue 4 (EYA4) is silenced in pancreatic ductal adenocarcinoma (PDAC) and functions as a tumor suppressor to restrain PDAC development, albeit the molecular mechanism underlying its downregulation remains enigmatic. Methods: Functional studies were determined by immunohistochemistry of PDAC samples from patients and Pdx1-Cre; LSL-KrasG12D/+; Trp53fl/+ (KPC) mice, three-dimensional spheroid culture, flow cytometry, MTT and subcutaneous xenograft experiments. Mechanistical studies were examined by cellular ubiquitination, cycloheximide (CHX) pulse-chase, co-immunoprecipitation, chromatin immunoprecipitation, GST-pulldown, in vitro protein kinase assay, immunofluorescence and luciferase reporter assays. Results: We screen E3 ligase that is negatively correlated with EYA4 and uncover a mutually exclusive interaction of tripartite motif containing 69 (TRIM69) with EYA4 in human PDAC. TRIM69 elicits EYA4 polyubiquitylation and turnover independent of P53 and impedes the EYA4-driven deactivation of ß-catenin/ID2 cascade, fueling PDAC cell proliferation in vitro and tumor development in mice. Expression of TRIM69 is upregulated in PDAC samples from independent cohorts of patients and the Pdx1-Cre; LSL-KrasG12D/+; Trp53fl/+ (KPC) mice, and associated with unfavorable prognosis. Depleting TRIM69 preferentially induces lethality in the EYA4-deficient PDAC cells. We further unearth that ERK2 directly binds to the D-site of mitogen-activated protein kinase (MAPK) docking groove in EYA4 Leu512/514 and phosphorylates EYA4 at Ser37, which is instrumental for EYA4 polyubiquitylation and turnover by TRIM69. Conclusion: Our results define a previously unappreciated role of TRIM69-EYA4 axis in pancreatic tumorigenesis and underscore that targeting TRIM69 might be an effective therapeutic approach for PDAC harboring EYA4 deficiency.

LUBAC regulates ciliogenesis by promoting CP110 removal from the mother centriole.

Primary cilia transduce diverse signals in embryonic development and adult tissues. Defective ciliogenesis results in a series of human disorders collectively known as ciliopathies. The CP110-CEP97 complex removal from the mother centriole is an early critical step for ciliogenesis, but the underlying mechanism for this step remains largely obscure. Here, we reveal that the linear ubiquitin chain assembly complex (LUBAC) plays an essential role in ciliogenesis by targeting the CP110-CEP97 complex. LUBAC specifically generates linear ubiquitin chains on CP110, which is required for CP110 removal from the mother centriole in ciliogenesis. We further identify that a pre-mRNA splicing factor, PRPF8, at the distal end of the mother centriole acts as the receptor of the linear ubiquitin chains to facilitate CP110 removal at the initial stage of ciliogenesis. Thus, our study reveals a direct mechanism of regulating CP110 removal in ciliogenesis and implicates the E3 ligase LUBAC as a potential therapy target of cilia-associated diseases, including ciliopathies and cancers.

A single-cell atlas of liver metastases of colorectal cancer reveals reprogramming of the tumor microenvironment in response to preoperative chemotherapy.

Metastasis is the primary cause of cancer-related mortality in colorectal cancer (CRC) patients. How to improve therapeutic options for patients with metastatic CRC is the core question for CRC treatment. However, the complexity and diversity of stromal context of the tumor microenvironment (TME) in liver metastases of CRC have not been fully understood, and the influence of stromal cells on response to chemotherapy is unclear. Here we performed an in-depth analysis of the transcriptional landscape of primary CRC, matched liver metastases and blood at single-cell resolution, and a systematic examination of transcriptional changes and phenotypic alterations of the TME in response to preoperative chemotherapy (PC). Based on 111,292 single-cell transcriptomes, our study reveals that TME of treatment-naïve tumors is characterized by the higher abundance of less-activated B cells and higher heterogeneity of tumor-associated macrophages (TAMs). By contrast, in tumors treated with PC, we found activation of B cells, lower diversity of TAMs with immature and less activated phenotype, lower abundance of both dysfunctional T cells and ECM-remodeling cancer-associated fibroblasts, and an accumulation of myofibroblasts. Our study provides a foundation for future investigation of the cellular mechanisms underlying liver metastasis of CRC and its response to PC, and opens up new possibilities for the development of therapeutic strategies for CRC.

Crosstalk between hypoxia-sensing ULK1/2 and YAP-driven glycolysis fuels pancreatic ductal adenocarcinoma development.

Autophagy and glycolysis are two catabolic processes that manipulate pancreatic ductal adenocarcinoma (PDAC) development in response to hypoxia sensing, yet the underlying mechanism of how they are interlinked remain elusive. Methods: The functional roles of Unc-51 like kinase 1 and 2 (ULK1/2) in pyruvate kinase M2 (PKM2) transcription and glycolysis under hypoxia were assessed by chromatin immunoprecipitation, luciferase reporter, glucose consumption and lactate production assay. Co-immunoprecipitation, cellular ubiquitination, His-pulldown, in vitro protein kinase assay, immunofluorescence, immunohistochemistry, CRISPR technology, in silico studies were adopted to determine the molecular mechanism. Correlation analyses were performed in KPC (Pdx1-Cre; LSL-KrasG12D/+; Trp53fl/+) mice and clinical samples from PDAC patients. Therapeutic potential of ULK1/2 inhibitor and 2-deoxyglucose (2-DG) or 3-bromopyruvate (3-BP) was evaluated in cell-derived xenograft (CDX) and the patient-derived xenograft (PDX) models of nude mice. Results: ULK1/2, but not ULK3, augments hypoxic glycolysis in PDAC cells mediated by PKM2 independent of BCL2/adenovirus E1B 19 kDa interacting protein 3 (BNIP3). Mechanistically, hypoxia stimulates ULK1 to translocate into nucleus, where it interacts with and phosphorylates yes-associated protein (YAP) at Ser227, resulting in YAP stabilization through blockade of ubiquitin-proteasome system (UPS), which in turn facilitates PKM2 transcription, glycolysis, cell proliferation in vitro as well as PDAC growth in mice. ULK1/2 is positively correlated with YAP and PKM2 in tumor tissues from KPC mice and clinical samples from PDAC patients. Pharmacological deactivation of ULK1/2 potentiates the antineoplastic efficacy of 2-DG and 3-BP in CDX and PDX models. Conclusion: Our findings underscore the Ser227 autophosphorylation-dependent nuclear YAP stabilization as a central node that couples ULK1/2-initiated autophagy to hypoxic glycolysis during PDAC development and propose that targeting ULK1/2 combined with 2-DG or 3-BP might be a feasible therapeutic strategy against PDAC.

LPA signaling acts as a cell-extrinsic mechanism to initiate cilia disassembly and promote neurogenesis.

Dynamic assembly and disassembly of primary cilia controls embryonic development and tissue homeostasis. Dysregulation of ciliogenesis causes human developmental diseases termed ciliopathies. Cell-intrinsic regulatory mechanisms of cilia disassembly have been well-studied. The extracellular cues controlling cilia disassembly remain elusive, however. Here, we show that lysophosphatidic acid (LPA), a multifunctional bioactive phospholipid, acts as a physiological extracellular factor to initiate cilia disassembly and promote neurogenesis. Through systematic analysis of serum components, we identify a small molecular-LPA as the major driver of cilia disassembly. Genetic inactivation and pharmacological inhibition of LPA receptor 1 (LPAR1) abrogate cilia disassembly triggered by serum. The LPA-LPAR-G-protein pathway promotes the transcription and phosphorylation of cilia disassembly factors-Aurora A, through activating the transcription coactivators YAP/TAZ and calcium/CaM pathway, respectively. Deletion of Lpar1 in mice causes abnormally elongated cilia and decreased proliferation in neural progenitor cells, thereby resulting in defective neurogenesis. Collectively, our findings establish LPA as a physiological initiator of cilia disassembly and suggest targeting the metabolism of LPA and the LPA pathway as potential therapies for diseases with dysfunctional ciliogenesis.

Hedgehog Signaling, a Critical Pathway Governing the Development and Progression of Hepatocellular Carcinoma.

Hedgehog (Hh) signaling is a classic morphogen in controlling embryonic development and tissue repairing. Aberrant activation of Hh signaling has been well documented in liver cancer, including hepatoblastoma, hepatocellular carcinoma (HCC) and cholangiocarcinoma. The present review aims to update the current understanding on how abnormal Hh signaling molecules modulate initiation, progression, drug resistance and metastasis of HCC. The latest relevant literature was reviewed with our recent findings to provide an overview regarding the molecular interplay and clinical relevance of the Hh signaling in HCC management. Hh signaling molecules are involved in the transformation of pre-carcinogenic lesions to malignant features in chronic liver injury, such as nonalcoholic steatohepatitis. Activation of GLI target genes, such as ABCC1 and TAP1, is responsible for drug resistance in hepatoma cells, with a CD133-/EpCAM- surface molecular profile, and GLI1 and truncated GLI1 account for the metastatic feature of the hepatoma cells, with upregulation of matrix metalloproteinases. A novel bioassay for the Sonic Hh ligand in tissue specimens may assist HCC diagnosis with negative α-fetoprotein and predict early microvascular invasion. In-depth exploration of the Hh signaling deepens our understanding of its molecular modulation in HCC initiation, drug sensitivity and metastasis, and guides precise management of HCC on an individual basis.

CEP55 promotes cilia disassembly through stabilizing Aurora A kinase.

Primary cilia protrude from the cell surface and have diverse roles during development and disease, which depends on the precise timing and control of cilia assembly and disassembly. Inactivation of assembly often causes cilia defects and underlies ciliopathy, while diseases caused by dysfunction in disassembly remain largely unknown. Here, we demonstrate that CEP55 functions as a cilia disassembly regulator to participate in ciliopathy. Cep55-/- mice display clinical manifestations of Meckel-Gruber syndrome, including perinatal death, polycystic kidneys, and abnormalities in the CNS. Interestingly, Cep55-/- mice exhibit an abnormal elongation of cilia on these tissues. Mechanistically, CEP55 promotes cilia disassembly by interacting with and stabilizing Aurora A kinase, which is achieved through facilitating the chaperonin CCT complex to Aurora A. In addition, CEP55 mutation in Meckel-Gruber syndrome causes the failure of cilia disassembly. Thus, our study establishes a cilia disassembly role for CEP55 in vivo, coupling defects in cilia disassembly to ciliopathy and further suggesting that proper cilia dynamics are critical for mammalian development.

Development of a high-strength Zn-Mn-Mg alloy for ligament reconstruction fixation.

Although various biodegradable materials have been investigated for ligament reconstruction fixation in the past decades, only few of them possess a combination of high mechanical properties, appropriate degradation rate, good biocompatibility, and osteogenic effect, thus limiting their clinical applications. A high-strength Zn-0.8Mn-0.4Mg alloy (i.e., Zn08Mn04Mg) with yield strength of 317 MPa was developed to address this issue. The alloy showed good biocompatibility and promising osteogenic effect in vitro. The degradation effects of Zn08Mn04Mg interference screws on the interface between soft tissue and bone were investigated in anterior cruciate ligament (ACL) reconstruction in rabbits. Compared to Ti6Al4V, the Zn alloy screws significantly accelerated the formation of new bone and further induced partial tendon mineralization, which promoted tendon-bone integration. The newly developed screws are believed to facilitate early joint function recovery and rehabilitation training and also avoid screw breakage during insertion, thereby contributing to an extensive clinical prospect.

Novel aptasensor-based assay of sonic hedgehog ligand for detection of portal vein invasion of hepatocellular carcinoma.

The high expression of sonic hedgehog ligand (SHh) is closely correlated to the metastasis, drug resistance and poor prognosis of hepatocellular carcinoma (HCC). Therefore, sensitive, specific and efficient detection methods for SHh are needed for the early diagnosis and assessment of prognosis. Herein, an aptamer, AP32 that specifically binds to SHh (KD = 25.7 ± 4.1 nM) was obtained by SELEX technology with further optimization. In vivo experiments confirmed that AP32 has the potential to be an imaging probe for Huh-7 cell-derived xenograft. The interaction mode in 3-dimensional configuration between the aptamer and SHh was established by molecular simulation and confirmed by mutations at key sites of the aptamer. An aptasensor-based assay was successfully developed by conjugating Texas-Red-labeled AP32 to microbeads, and was used to analyze SHh content in hepatoma cell lysates, serum and HCC specimens. The method exhibited a broad detection range from 0.07 to 62.5 nM with a low detection limit of 69 pM, and a recovery rate of 104.6 ± 3.9% in serum. When the assay was used to measure SHh content in tissue lysates, the results demonstrated that it possessed 57.1% positivity, 100% specificity in distinguishing 28 HCC specimens from normal tissues, and was compensatory for detection of HCC in AFP-negative cases. Moreover, elevated SHh levels are indicative of portal vein invasion at 77.8% positive rate. This novel aptasensor-based SHh assay may offer a reliable means in predicting early metastasis and poor prognosis in hepatocellular carcinoma.

Immunotherapy for advanced hepatocellular carcinoma, where are we?

A couple of molecular-targeting medications, such as Lenvatinib, are available for the treatment of hepatocellular carcinoma (HCC) in addition to Sorafenib in an advanced stage. Approval for the use of immune check-point inhibitors, such as Nivolumab and Pembrolizumab has shifted the paradigm of current HCC treatment, and the monotherapy or in combination with Lenvatinib or Sorafenib has significantly extended overall survival or progression-free survival in a large portion of patients. A combination of programmed cell death ligand-1 (PD-L1) inhibitor Atezolizumab with a vascular endothelial growth factor (VEGF) inhibitor, Bevacizumab, has recently achieved promising outcome in unresectable HCC patients. Other immunotherapy, such as chimeric antigen receptor T (CAR-T) cell therapy has achieved an evolutional success in hematologic malignancies, and has extended its use in deadly solid tumors, such as HCC. Although there exist various barriers, novel approaches are developed to move potential adoptive T cell therapy strategies, including cytokine-induced killer (CIK) cells, tumor-infiltrating lymphocytes (TIL), T cell receptor (TCR) T cells, CAR-T cells, to clinical application.

Advances in detection of infectious agents by aptamer-based technologies.

Infectious diseases still remain one of the biggest challenges for human health. Accurate and early detection of infectious pathogens are crucial for transmission control, clinical diagnosis, and therapy. For a traditional reason, most immunological and microbiological laboratories are equipped with instruments designated for antibody-based assays in detection of infectious pathogens or clinical diagnosis. Emerging aptamer-based technologies have pushed a shift from antibody-based to aptamer-based assays due to equal specificity, even better sensitivity, lower manufacturing cost and more flexibility in amending for chemiluminescent, electrochemical or fluorescent detection in a multifaceted and high throughput fashion in comparison of aptamer-based to antibody-based assays. The nature of aptamer-based technologies is particularly suitable for point-of-care testing in remote areas at warm or hot atmosphere, and mass screening for potential infection in pandemic of emerging infectious agents, such as SARS-CoV or SARS-CoV-2 in an epicentre or other regions. This review intends to summarize currently available aptamer-based technologies in detection of bacterial, viral, and protozoan pathogens for research and clinical application. It is anticipated that potential technologies will be further optimized and validated for clinical translation in meeting increasing demands for prompt, precise, and reliable detection of specific pathogens in various atmospheric conditions.

Design biodegradable Zn alloys: Second phases and their significant influences on alloy properties.

Alloying combined with plastic deformation processing is widely used to improve mechanical properties of pure Zn. As-cast Zn and its alloys are brittle. Beside plastic deformation processing, no effective method has yet been found to eliminate the brittleness and even endow room temperature super-ductility. Second phase, induced by alloying, not only largely determines the ability of plastic deformation, but also influences strength, corrosion rate and cytotoxicity. Controlling second phase is important for designing biodegradable Zn alloys. In this review, knowledge related to second phases in biodegradable Zn alloys has been analyzed and summarized, including characteristics of binary phase diagrams, volume fraction of second phase in function of atomic percentage of an alloying element, and so on. Controversies about second phases in Zn-Li, Zn-Cu and Zn-Fe systems have been settled down, which benefits future studies. The effects of alloying elements and second phases on microstructure, strength, ductility, corrosion rate and cytotoxicity have been neatly summarized. Mg, Mn, Li, Cu and Ag are recommended as the major alloying elements, owing to their prominent beneficial effects on at least one of the above properties. In future, synergistic effects of these elements should be more thoroughly investigated. For other nutritional elements, such as Fe and Ca, refining second phase is a matter of vital concern.

Hedgehog signalling mediates drug resistance through targeting TAP1 in hepatocellular carcinoma.

Multidrug resistance is one of the reasons for low survival of advanced hepatocellular carcinoma (HCC). Our previous studies indicate that the hedgehog signalling is involved in hepatic carcinogenesis, metastasis and chemo-resistance. The present study aims to uncover molecular mechanisms underlying hepatoma chemo-resistance. TAP1 and GLI1/2 gene expression was assessed in both poorly differentiated hepatoma cells and HCC specimens. Potential GLI-binding site in the TAP1 promoter sequence was validated by molecular assays. Approximately 75% HCC specimens exhibited an elevated expression of hedgehog GLI1 transcription factor compared with adjacent liver tissue. Both GLI1/2 and TAP1 protein levels were significantly elevated in poorly differentiated hepatoma cells. Both Huh-7-trans and Huh-7-DN displayed more karyotypic abnormalities and differential gene expression profiles than their native Huh-7 cells. Sensitivity to Sorafenib, doxorubicin and cisplatin was remarkably improved after either GLI1 or TAP1 gene was inhibited by an RNAi approach or by a specific GLI1/2 inhibitor, GANT61. Further experiments confirmed that hedgehog transcription factor GLI1/2 binds to the TAP1 promoter, indicating that TAP1 is one of GLI1/2 target genes. In conclusion, TAP1 is under direct transcriptional control of the hedgehog signalling. Targeting hedgehog signalling confers a novel insight into alleviating drug resistance in the treatment of refractory HCC.

Rab7 regulates primary cilia disassembly through cilia excision.

The primary cilium is a sensory organelle that protrudes from the cell surface. Primary cilia undergo dynamic transitions between assembly and disassembly to exert their function in cell signaling. In this study, we identify the small GTPase Rab7 as a novel regulator of cilia disassembly. Depletion of Rab7 potently induced spontaneous ciliogenesis in proliferating cells and promoted cilia elongation during quiescence. Moreover, Rab7 performs an essential role in cilia disassembly; knockdown of Rab7 blocked serum-induced ciliary resorption, and active Rab7 was required for this process. Further, we demonstrate that Rab7 depletion significantly suppresses cilia tip excision, referred to as cilia ectocytosis, which has been identified as required for cilia disassembly. Mechanically, the failure of F-actin polymerization at the site of excision of cilia tips caused suppression of cilia ectocytosis on Rab7 depletion. Overall, our results suggest a novel function for Rab7 in regulating cilia ectocytosis and cilia disassembly via control of intraciliary F-actin polymerization.

MAVS O-GlcNAcylation Is Essential for Host Antiviral Immunity against Lethal RNA Viruses.

It is known that lethal viruses profoundly manipulate host metabolism, but how the metabolism alternation affects the immediate host antiviral immunity remains elusive. Here, we report that the O-GlcNAcylation of mitochondrial antiviral-signaling protein (MAVS), a key mediator of interferon signaling, is a critical regulation to activate the host innate immunity against RNA viruses. We show that O-GlcNAcylation depletion in myeloid cells renders the host more susceptible to virus infection both in vitro and in vivo. Mechanistically, we demonstrate that MAVS O-GlcNAcylation is required for virus-induced MAVS K63-linked ubiquitination, thereby facilitating IRF3 activation and IFNß production. We further demonstrate that D-glucosamine, a commonly used dietary supplement, effectively protects mice against a range of lethal RNA viruses, including human influenza virus. Our study highlights a critical role of O-GlcNAcylation in regulating host antiviral immunity and validates D-glucosamine as a potential therapeutic for virus infections.

Phosphorylation of 14-3-3ζ links YAP transcriptional activation to hypoxic glycolysis for tumorigenesis.

Hypoxic microenvironment deregulates metabolic homeostasis in cancer cells albeit the underlying mechanisms involved in this process remain hitherto enigmatic. 14-3-3ζ/Yes-associated protein (YAP) axis plays a principal role in malignant transformation and tumor development. Here, we report that hypoxia disassembles 14-3-3ζ from YAP and thereby promotes YAP nuclear localization mediated by ERK2, which directly binds to the D-site of mitogen-activated protein kinase (MAPK) docking domain in 14-3-3ζ Leu98/100 and phosphorylates 14-3-3ζ at Ser37. When localizing in nucleus, YAP recruits at pyruvate kinase M2 (PKM2) gene promoter with hypoxia-inducible factor 1α (HIF-1α), for which PKM2 transcription is required. 14-3-3ζ Ser37 phosphorylation is instrumental for the hypoxia-induced glucose uptake, lactate production, and clonogenicity of pancreatic ductal adenocarcinoma (PDAC) cells, as well as tumorigenesis in mice. The 14-3-3ζ Ser37 phosphorylation positively correlates with p-ERK1/2 activity and HIF-1α expression in clinical samples from patients with PDAC and predicts unfavorable prognosis. Our findings underscore an appreciable linkage between YAP transcriptional activation and hypoxic glycolysis governed by ERK2-dependent 14-3-3ζ Ser37 phosphorylation for malignant progression of PDAC.

AMPK-mediated activation of MCU stimulates mitochondrial Ca2+ entry to promote mitotic progression.

The capacity of cells to alter bioenergetics in response to the demands of various biological processes is essential for normal physiology. The coordination of energy sensing and production with highly energy-demanding cellular processes, such as cell division, is poorly understood. Here, we show that a cell cycle-dependent mitochondrial Ca2+ transient connects energy sensing to mitochondrial activity for mitotic progression. The mitochondrial Ca2+ uniporter (MCU) mediates a rapid mitochondrial Ca2+ transient during mitosis. Inhibition of mitochondrial Ca2+ transients via MCU depletion causes spindle checkpoint-dependent mitotic delay. Cellular ATP levels drop during early mitosis, and the mitochondrial Ca2+ transients boost mitochondrial respiration to restore energy homeostasis. This is achieved through mitosis-specific MCU phosphorylation and activation by the mitochondrial translocation of energy sensor AMP-activated protein kinase (AMPK). Our results establish a critical role for AMPK- and MCU-dependent mitochondrial Ca2+ signalling in mitosis and reveal a mechanism of mitochondrial metabolic adaptation to acute cellular energy stress.