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1. Peroxisomal import stress activates integrated stress response and inhibits ribosome biogenesis

   https://doi.org/10.1093/pnasnexus/pgae429  

   Kim, Jinoh; Huang, Kerui; Vo, Pham_Thuy Tien; Miao, Ting; Correia, Jacinta; Kumar, Ankur; Simons, Mirre_J P; Bai, Hua (October 2024, PNAS Nexus)

   Metallo, Christian (Ed.)

   Abstract Impaired organelle-specific protein import triggers a variety of cellular stress responses, including adaptive pathways to balance protein homeostasis. Most of the previous studies focus on the cellular stress response triggered by misfolded proteins or defective protein import in the endoplasmic reticulum or mitochondria. However, little is known about the cellular stress response to impaired protein import in the peroxisome, an understudied organelle that has recently emerged as a key signaling hub for cellular and metabolic homeostasis. To uncover evolutionarily conserved cellular responses upon defective peroxisomal import, we carried out a comparative transcriptomic analysis on fruit flies with tissue-specific peroxin knockdown and human HEK293 cells expressing dominant-negative PEX5C11A. Our RNA-seq results reveal that defective peroxisomal import upregulates integrated stress response (ISR) and downregulates ribosome biogenesis in both flies and human cells. Functional analyses confirm that impaired peroxisomal import induces eIF2α phosphorylation and ATF4 expression. Loss of ATF4 exaggerates cellular damage upon peroxisomal import defects, suggesting that ATF4 activation serves as a cellular cytoprotective mechanism upon peroxisomal import stress. Intriguingly, we show that peroxisomal import stress decreases the expression of rRNA processing genes and inhibits early pre-rRNA processing, which leads to the accumulation of 47S precursor rRNA and reduction of downstream rRNA intermediates. Taken together, we identify ISR activation and ribosome biogenesis inhibition as conserved adaptive stress responses to defective peroxisomal import and uncover a novel link between peroxisomal dysfunction and rRNA processing. 

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2. Aging impairs peroxisome biogenesis in human B cells

   https://doi.org/10.1093/gerona/glaf148  

   Correia, Jacinta; Roy, Promit Sinha; Holden, Kaitlyn G; Kohut, Marian L; Bai, Hua (January 2026, The Journals of Gerontology, Series A: Biological Sciences and Medical Sciences)

   Duque, Gustavo (Ed.)

   Abstract Emerging evidence highlights the critical role of cellular metabolism in immune cell activation, development, and function. Peroxisomes, key metabolic organelles, maintain metabolic homeostasis, yet their role in immune cells remains underexplored. While animal studies show age-related declines in peroxisome biogenesis, this process is unconfirmed in human aging. We investigated peroxisome biogenesis in human peripheral blood mononuclear cells (PBMCs) and found a significant decline in aged CD19+ B cells compared to CD4+ T cells, CD8+ T cells, and CD14+ monocytes. B cell aging also reduces peroxisomal matrix enzyme import, evidenced by decreased SKL-containing enzymes and mature ACOX1, alongside downregulation of PEX19 and E3 ubiquitin ligases PEX2, PEX10, and PEX12. These findings confirm an evolutionarily conserved and age-related decline in peroxisome biogenesis. Further, our work unveils cell type-specific changes in aging human PBMCs, and provides new insights into peroxisome-mediated immunometabolism and B cell aging. 

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3. Visualizing the dynamics of plant energy organelles

   https://doi.org/10.1042/BST20221093  

   Koenig, Amanda M; Liu, Bo; Hu, Jianping (November 2023, Biochemical Society Transactions)

   Plant organelles predominantly rely on the actin cytoskeleton and the myosin motors for long-distance trafficking, while using microtubules and the kinesin motors mostly for short-range movement. The distribution and motility of organelles in the plant cell are fundamentally important to robust plant growth and defense. Chloroplasts, mitochondria, and peroxisomes are essential organelles in plants that function independently and coordinately during energy metabolism and other key metabolic processes. In response to developmental and environmental stimuli, these energy organelles modulate their metabolism, morphology, abundance, distribution and motility in the cell to meet the need of the plant. Consistent with their metabolic links in processes like photorespiration and fatty acid mobilization is the frequently observed inter-organellar physical interaction, sometimes through organelle membranous protrusions. The development of various organelle-specific fluorescent protein tags has allowed the simultaneous visualization of organelle movement in living plant cells by confocal microscopy. These energy organelles display an array of morphology and movement patterns and redistribute within the cell in response to changes such as varying light conditions, temperature fluctuations, ROS-inducible treatments, and during pollen tube development and immune response, independently or in association with one another. Although there are more reports on the mechanism of chloroplast movement than that of peroxisomes and mitochondria, our knowledge of how and why these three energy organelles move and distribute in the plant cell is still scarce at the functional and mechanistic level. It is critical to identify factors that control organelle motility coupled with plant growth, development, and stress response. 

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4. Vacuolar degradation of plant organelles

   https://doi.org/10.1093/plcell/koae128  

   Otegui, Marisa S; Steelheart, Charlotte; Ma, Wenlong; Ma, Juncai; Kang, Byung-Ho; De_Medina_Hernandez, Victor Sanchez; Dagdas, Yasin; Gao, Caiji; Goto-Yamada, Shino; Oikawa, Kazusato; et al (April 2024, The Plant Cell)

   Abstract Plants continuously remodel and degrade their organelles due to damage from their metabolic activities and environmental stressors, as well as an integral part of their cell differentiation programs. Whereas certain organelles use local hydrolytic enzymes for limited remodeling, most of the pathways that control the partial or complete dismantling of organelles rely on vacuolar degradation. Specifically, selective autophagic pathways play a crucial role in recognizing and sorting plant organelle cargo for vacuolar clearance, especially under cellular stress conditions induced by factors like heat, drought, and damaging light. In these short reviews, we discuss the mechanisms that control the vacuolar degradation of chloroplasts, mitochondria, endoplasmic reticulum, Golgi, and peroxisomes, with an emphasis on autophagy, recently discovered selective autophagy receptors for plant organelles, and crosstalk with other catabolic pathways. 

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5. Multifactorial analysis of simultaneous organelle movement reveals cell-specific motility of peroxisomes and mitochondria

   https://doi.org/10.1093/plphys/kiag119  

   Koenig, Amanda M; Krawczyk, Katarzyna; Huang, Calvin H; Lee, Yuh-Ru Julie; Liu, Bo; Hu, Jianping (March 2026, Plant Physiology)

   Abstract The movement, distribution, and interactions of organelles are cell-type specific, responding to fluctuating metabolic and environmental cues and governing the efficiency of plant physiology and stress response. The directional motility of various plant organelles is predominantly driven by the actomyosin system, yet the distinct functionality of these organelles across plant tissues presupposes organelle-specific regulation of motility, which requires the detection of subtle shifts in dynamics. Meanwhile, studies that comprehensively characterize and directly compare the simultaneous movement of multiple types of organelles within the same cell are limited. Here, we visualized peroxisomes, mitochondria, chloroplasts, Golgi bodies, and actin filaments simultaneously in tobacco (Nicotiana tabacum) to evaluate organelle organization and motility within the context of one another. Quantitative analysis of multiple motility factors enabled us to identify peroxisome motility in tobacco mesophyll as distinct from other organelles. Further analysis in Arabidopsis (Arabidopsis thaliana) revealed that both mitochondria and peroxisomes are slower in mesophyll cells compared to epidermis in normal growth conditions, but their motility patterns are unique from one another across leaf tissue after plants experienced conditions that induce photorespiration, a metabolic pathway requiring the concerted action of chloroplasts, peroxisomes, and mitochondria. Our quantitative analysis of thousands of organelles across species, cell type, and physiological conditions unveils distinct modulation of motility according to organelle identity and function. The extensive combinatorial characterizations of plant organelle movement provide a fundamental resource for the future discovery of molecular mechanisms driving the movement and distribution of diverse organelles. 

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