bims-lypmec 2023-10-01 papers

J Mol Biol. 2023 Sep 27. pii: S0022-2836(23)00404-7. [Epub ahead of print] 168293

Mechanistic insights into the interactions of Arl8b with the RUN domains of PLEKHM1 and SKIP.

Xiaohui Qiu, Ying Li, Yingli Wang, Xinyu Gong, Yaru Wang, Lifeng Pan.

Arl8b, a specific Arf-like family GTPase present on lysosome, and plays critical roles in many lysosome-related cellular processes such as autophagy. The active Arl8b can be specifically recognized by the RUN domains of two Arl8b-effectors PLEKHM1 and SKIP, thereby regulating the autophagosome/lysosome membrane fusion and the intracellular lysosome positioning, respectively. However, the mechanistic bases underlying the interactions of Arl8b with the RUN domains of PLEKHM1 and SKIP remain elusive. Here, we report the two high-resolution crystal structures of the active Arl8b in complex with the RUN domains of PLEKHM1 and SKIP. In addition to elucidating the detailed molecular mechanism governing the specific interactions of the active Arl8b with the RUN domains of PLEKHM1 and SKIP, the determined complex structures also reveal a general binding mode shared by the PLEKHM1 and SKIP RUN domains for interacting with the active Arl8b. Furthermore, we uncovered a competitive relationship between the RUN domains of PLEKHM1 and SKIP in binding to the active Arl8b as well as a unique small GTPase-binding mode adopted by the PLEKHM1 and SKIP RUN domains, thereby enriching the repertoire of the RUN domain/small GTPase interaction modes. In all, our findings provide new mechanistic insights into the interactions of the active Arl8b with PLEKHM1 and SKIP, and are valuable for further understanding the working modes of these proteins in relevant cellular processes.

Keywords: Arl8b; Lysosome; PLEKHM1; RUN domain; SKIP

DOI: https://doi.org/10.1016/j.jmb.2023.168293

Molecules. 2023 Sep 15. pii: 6650. [Epub ahead of print]28(18):

Recent Development of Lysosome-Targeted Organic Fluorescent Probes for Reactive Oxygen Species.

Van-Nghia Nguyen, Haidong Li.

Reactive oxygen species (ROS) are extremely important for various biological functions. Lysosome plays key roles in cellular metabolism and has been known as the stomach of cells. The abnormalities and malfunctioning of lysosomal function are associated with many diseases. Accordingly, the quantitative monitoring and real-time imaging of ROS in lysosomes are of great interest. In recent years, with the advancement of fluorescence imaging, fluorescent ROS probes have received considerable interest in the biomedical field. Thus far, considerable efforts have been undertaken to create synthetic fluorescent probes for sensing ROS in lysosomes; however, specific review articles on this topic are still lacking. This review provides a general introduction to fluorescence imaging technology, the sensing mechanisms of fluorescent probes, lysosomes, and design strategies for lysosome-targetable fluorescent ROS probes. In addition, the latest advancements in organic small-molecule fluorescent probes for ROS detection within lysosomes are discussed. Finally, the main challenges and future perspectives for developing effective lysosome-targetable fluorescent ROS probes for biomedical applications are presented.

Keywords: ROS; ROS detection; fluorescence imaging; fluorescent probes; lysosome

DOI: https://doi.org/10.3390/molecules28186650

Nature. 2023 Sep 27.

Proteome census upon nutrient stress reveals Golgiphagy membrane receptors.

Kelsey L Hickey, Sharan Swarup, Ian R Smith, Julia C Paoli, Enya Miguel Whelan, Joao A Paulo, J Wade Harper.

During nutrient stress, macroautophagy degrades cellular macromolecules, thereby providing biosynthetic building blocks while simultaneously remodeling the proteome1,2. While machinery responsible for initiation of macroautophagy is well characterized3,4, our understanding of the extent to which individual proteins, protein complexes and organelles are selected for autophagic degradation, and the underlying targeting mechanisms is limited. Here, we use orthogonal proteomic strategies to provide a spatial proteome census of autophagic cargo during nutrient stress in mammalian cells. We find that macroautophagy has selectivity for recycling membrane-bound organelles (principally Golgi and ER). Through autophagic cargo prioritization, we identify a complex of membrane-embedded proteins, YIPF3 and YIPF4, as receptors for Golgiphagy. During nutrient stress, YIPF3 and YIPF4 interact with ATG8s via LIR motifs and are mobilized into autophagosomes that traffic to lysosomes in a process that requires the canonical autophagic machinery. Cells lacking YIPF3 or YIPF4 are selectively defective in elimination of a specific cohort of Golgi membrane proteins during nutrient stress. Moreover, YIPF3/4 play an analogous role in Golgi remodeling during programmed conversion of stem cells to the neuronal lineage in vitro. Collectively, this study reveals prioritization of membrane protein cargo during nutrient stress-dependent proteome remodeling and identifies an unanticipated Golgi remodeling pathway requiring membrane-embedded receptors.

DOI: https://doi.org/10.1038/s41586-023-06657-6

Biology (Basel). 2023 Aug 23. pii: 1159. [Epub ahead of print]12(9):

Omics-Based Approaches for the Characterization of Pompe Disease Metabolic Phenotypes.

Nuria Gómez-Cebrián, Elena Gras-Colomer, José Luis Poveda Andrés, Antonio Pineda-Lucena, Leonor Puchades-Carrasco.

Lysosomal storage disorders (LSDs) constitute a large group of rare, multisystemic, inherited disorders of metabolism, characterized by defects in lysosomal enzymes, accessory proteins, membrane transporters or trafficking proteins. Pompe disease (PD) is produced by mutations in the acid alpha-glucosidase (GAA) lysosomal enzyme. This enzymatic deficiency leads to the aberrant accumulation of glycogen in the lysosome. The onset of symptoms, including a variety of neurological and multiple-organ pathologies, can range from birth to adulthood, and disease severity can vary between individuals. Although very significant advances related to the development of new treatments, and also to the improvement of newborn screening programs and tools for a more accurate diagnosis and follow-up of patients, have occurred over recent years, there exists an unmet need for further understanding the molecular mechanisms underlying the progression of the disease. Also, the reason why currently available treatments lose effectiveness over time in some patients is not completely understood. In this scenario, characterization of the metabolic phenotype is a valuable approach to gain insights into the global impact of lysosomal dysfunction, and its potential correlation with clinical progression and response to therapies. These approaches represent a discovery tool for investigating disease-induced modifications in the complete metabolic profile, including large numbers of metabolites that are simultaneously analyzed, enabling the identification of novel potential biomarkers associated with these conditions. This review aims to highlight the most relevant findings of recently published omics-based studies with a particular focus on describing the clinical potential of the specific metabolic phenotypes associated to different subgroups of PD patients.

Keywords: Pompe disease; glycogen storage disease; lysosomal storage disorders; metabolic phenotype; multi-omics; omics

DOI: https://doi.org/10.3390/biology12091159

Mol Cell. 2023 Sep 20. pii: S1097-2765(23)00695-0. [Epub ahead of print]

Lysosomal cyst(e)ine storage potentiates tolerance to oxidative stress in cancer cells.

Lixin He, Jinxin Chen, Pinwei Deng, Shumei Huang, Pian Liu, Chanjuan Wang, Xinjian Huang, Yue Li, Boyu Chen, Dongni Shi, Yunyun Xiao, Xiangfu Chen, Ying Ouyang, Libing Song, Chuyong Lin.

Cyst(e)ine is a key precursor for the synthesis of glutathione (GSH), which protects cancer cells from oxidative stress. Cyst(e)ine is stored in lysosomes, but its role in redox regulation is unclear. Here, we show that breast cancer cells upregulate major facilitator superfamily domain containing 12 (MFSD12) to increase lysosomal cyst(e)ine storage, which is released by cystinosin (CTNS) to maintain GSH levels and buffer oxidative stress. We find that mTORC1 regulates MFSD12 by directly phosphorylating residue T254, while mTORC1 inhibition enhances lysosome acidification that activates CTNS. This switch modulates lysosomal cyst(e)ine levels in response to oxidative stress, fine-tuning redox homeostasis to enhance cell fitness. MFSD12-T254A mutant inhibits MFSD12 function and suppresses tumor progression. Moreover, MFSD12 overexpression correlates with poor neoadjuvant chemotherapy response and prognosis in breast cancer patients. Our findings reveal the critical role of lysosomal cyst(e)ine storage in adaptive redox homeostasis and suggest that MFSD12 is a potential therapeutic target.

Keywords: CTNS; GSH; MFSD12; breast cancer; chemotherapy; cyst(e)ine; lysosome; mTORC1; oxidative stress; redox homeostasis

DOI: https://doi.org/10.1016/j.molcel.2023.08.032