Journal of biochemistry最新文献

Cisplatin-based chemotherapy is a standard treatment for non-small cell lung cancer (NSCLC), but drug resistance poses a major clinical challenge. Stress-adaptive mechanisms such as stress granule (SG) formation are increasingly recognized alternative pathways that facilitate cancer cell survival. Here, we identify the RNA-binding protein, family with sequence similarity 120A (FAM120A), as a SG-associated factor that drives cisplatin resistance in NSCLC. FAM120A expression was markedly elevated in cisplatin-resistant NSCLC cell lines and clinical tumor specimens, and was essential for SG formation and cell survival following cisplatin-induced stress. We found that the intrinsically disordered RNA-binding domain of FAM120A is essential for its incorporation into SGs and for its cytoprotective function. Using enhanced Cross-Linking Immunoprecipitation sequencing (eCLIP-seq) data and RNA immunoprecipitation-qPCR (RIP-qPCR), we identified the long noncoding RNA, metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) as a key FAM120A interacting partner. MALAT1 levels were reduced upon FAM120A depletion, and overexpression of MALAT1 was sufficient to restore cisplatin resistance in these cells. These findings suggest that MALAT1 is an RNA species that is stabilized by FAM120A and involved in the cellular response to chemotherapy. Targeting this regulatory mechanism may offer new therapeutic strategies to overcome cisplatin resistance in NSCLC.

Phospholipase A (PLA) and acyltransferases coordinate glycerophospholipid remodeling to maintain membrane diversity and function. The phospholipase A and acyltransferase (PLAAT) family combines PLA1/PLA2 with N- and O-acyltransferase activities, generating N-acylethanolamines with diverse bioactivities and enabling acyl-CoA-independent remodeling. PLAAT3 has been identified as a causative gene for human lipodystrophy. In addition to adipocyte dysfunction, PLAAT3-deficient mice develop cataracts due to impaired organelle degradation in lens fiber cells. In non-mammalian vertebrates such as zebrafish, which lack PLAAT3, PLAAT1 is highly expressed in the lens, and its deficiency similarly causes cataract-like abnormalities by blocking organelle clearance. A recent study reported that PLAAT1 promotes cardiolipin production in cultured cells, indicating a role in mitochondrial membrane lipid metabolism; however, its direct involvement in mitochondrial dynamics remains unclear. To address this, Sikder et al. (J. Biochem. 175:101-113, 2023) established a doxycycline-inducible mouse PLAAT1 expression system in HEK293 cells. Catalytically active PLAAT1 rapidly induced mitochondrial fragmentation and peroxisome loss, independently of changes in Drp1, Mfn2, and Opa1 expression. These findings reveal a previously unrecognized role of PLAAT1 in regulating organelle dynamics and maintaining cellular homeostasis.

The murine retrovirus integration site 1 (MRVI1) gene encodes an endoplasmic reticulum (ER)-associated membrane protein involved in calcium signalling, yet its molecular interaction network remains largely undefined. Here, we employed TurboID-based proximity labelling to construct the first comprehensive map of MRVI1-associated proteins in mammalian cells. This analysis identified >700 candidate interactors, including ER-localized factors and components of intracellular trafficking, consistent with the subcellular localization and signalling role of MRVI1. To investigate oncogenic modulation, we examined how co-expression of NPM-ALK-a constitutively active tyrosine kinase implicated in lymphoid malignancies-reshapes the MRVI1 interactome. Quantitative proteomics revealed that while the overall composition of MRVI1-associated proteins was largely preserved, a subset of interactions was selectively enhanced or attenuated by NPM-ALK. The association of MRVI1 with several signalling-related proteins was enhanced by NPM-ALK, including 12 proteins that have all been previously implicated in cancer-related pathways. In contrast, proteins whose interaction with MRVI1 was suppressed were functionally enriched in the Gene Ontology term 'negative regulation of apoptotic process'. Notably, anti-apoptotic regulators such as DDB1, PHB2 and NOTCH2 showed significantly reduced proximity labelling, suggesting that MRVI1 may participate in apoptosis-related networks disrupted during oncogenic transformation. Together, our findings demonstrate that MRVI1 forms a functionally diverse protein network that can be selectively remodelled by oncogenic signalling. This study not only uncovers potential mechanisms by which MRVI1 contributes to transformation but also provides a valuable proteomic resource for future investigation of MRVI1 function and regulation.

Microglia, the central nervous system's resident macrophages, are critical for immune defense, protecting neurons during infection. Their role in postnatal brain development, particularly after injury, remains unclear. Nucling, a protein up-regulated during cardiac muscle differentiation, regulates NF-κB, influencing apoptosis and cell proliferation. In this study, we examined the role of Nucling in microglial activation using wild-type (WT) and Nucling-knockout (KO) neonatal mice subjected to poly(I:C), a viral mimic. Poly(I:C) treatment increased Iba1-positive microglia in both genotypes; however, KO mice showed a significantly exaggerated response in both cortical and hippocampal regions. Furthermore, while proinflammatory M1 markers (iNOS, CD86, TNFα, IL-6) were upregulated in both WT and KO mice, the anti-inflammatory M2 marker Arginase 1 (Arg1) was induced in WT but significantly suppressed in KO mice, indicating impaired M2 polarization. These findings suggest that Nucling is essential for maintaining microglial polarization, supporting immunological processes against pathogens and aiding central nervous system development.

Autophagy is a conserved degradation process delivering intracellular components to lysosomes or vacuoles. Yeast studies have been pivotal in identifying autophagy-related (ATG) genes and defining the core machinery essential for autophagosome formation. A recent comprehensive analysis that systematically examined all atg mutants in S. cerevisiae under autophagy-inducing conditions revealed that mutants lacking Atg13, Atg8-conjugation, or Atg12-conjugation components retain partial activity in certain autophagy-related pathways, indicating that these core factors are not strictly essential for autophagy in yeast. In this commentary, we summarize how recent findings reshape our understanding of the flexibility in the essentiality of core autophagy factors and discuss the emerging importance of protein interaction-driven feedback in autophagy regulation.

Giant viruses encode unusual glycosylation machinery distinct from their amoebal hosts, raising fundamental questions about how their glycans are synthesized and diversified. Here we present a comparative glycomic analysis of mimivirus, tokyovirus, and hokutovirus, together with their common host Acanthamoeba castellanii. The main objective of this study was to determine whether giant viruses rely on host-derived N-glycosylation, or alternatively employ virus-encoded pathways to generate lineage-specific O-glycans, and to assess how these processes differ across virus families. N-glycan profiling revealed that all three viruses lack canonical eukaryotic core structures, in contrast to amoebal high-mannose N-glycans carrying pentose and phosphate residues. This finding demonstrates that giant viruses do not exploit the host secretory pathway for N-glycosylation, but instead depend on alternative mechanisms. O-glycan analyses showed lineage-specific patterns: family Marseilleviridae members tokyovirus and hokutovirus, displayed highly similar profiles, with minor virus-specific differences, whereas mimivirus exhibited structurally distinct glycans. Genomic inspection revealed that tokyovirus encodes only five glycosyltransferase-like genes, while A. castellanii harbors candidate enzymes for unusual monosaccharides. These findings clarify the distinct contributions of host and viral pathways and highlight evolutionary diversification of glycosylation among giant viruses.

Rab GTPases are molecular switches that control intracellular vesicular transport by cycling between GDP- and GTP-bound states. Insects encode an insect-specific subset, RabX; Bombyx mori RabX6 (BmRabX6) has been implicated in testis development and neuropeptide secretion, but its structure and mechanism were unknown. Here we report the 3.1 Å crystal structure of BmRabX6 in complex with GDP and Mg2+ (PDB: 9VLB), the first structure of an insect-specific Rab GTPase. BmRabX6 adopts the canonical small GTPase fold with conserved P-loop and Switch I/II, and displays a GDP-binding mode similar to vertebrate Rabs. Two features distinguish BmRabX6. First, the catalytic glutamine required for GTP hydrolysis in typical Rabs is naturally replaced by methionine (Met69) and oriented away from the nucleotide, consistent with obligate GAP-assisted hydrolysis. Second, one residue of the hydrophobic effector-binding triad is histidine (His47), suggesting a potential shift toward a hydrophilic interface-mediated interaction distinct from canonical Rab-effector recognition. AlphaFold3-based complex modeling further identified BmH9J2P5 as a prioritized GTPase-activating protein (GAP) candidate interacting with BmRabX6. These adaptations suggest that BmRabX6 preserves core nucleotide cycling while employing divergent regulatory chemistry tuned to insect physiology. Our structure provides a framework for testing GAP dependence and effector specificity of RabX6 in reproductive and neuronal tissues and illustrates how strategic amino-acid substitutions diversify Rab function.