bims-mecosi 2022-10-16 papers

Issue of 2022–10–16
five papers selected by
Verena Kohler, University of Graz

Methods Enzymol. 2022 ;pii: S0076-6879(22)00241-5. [Epub ahead of print]675 33-62

Reconstitution and biochemical studies of extended synaptotagmin-mediated lipid transport.

Ruyue He, Chenlu Li, Yinghui Liu, Haijia Yu.

Extended synaptotagmins (E-Syts) are a family of lipid transfer proteins (LTPs) located at the endoplasmic reticulum (ER)-plasma membrane (PM) contact sites in eukaryotic cells. They possess a conserved synaptotagmin-like mitochondrial-lipid-binding protein (SMP) domain and two to five C2 domains. While the membrane tethering function of E-Syts has been well studied in diverse species, recent studies revealed that the mammalian E-Syt1 and its yeast homolog tricalbin 3 (Tcb3) could transport lipids between the opposed membrane. Mechanical studies suggested SYT1 transfers lipids fundamentally through the SMP domain, but the lipid transport requires the regulation of C2 domain-mediated membrane tethering. In addition, both E-Syt1 and Tcb3 are Ca2+-modulated LTPs, which sense and interact with Ca2+ through the C2 domains. This chapter describes the in vitro reconstitution and biochemical assays for studying the functions and mechanisms of E-Syts, by expressing and purifying recombinant proteins, preparing reconstitution systems, and developing assays for membrane tethering and lipid transport.

Keywords: Calcium; Endoplasmic reticulum; Extended synaptotagmin; Lipid transfer; Liposome reconstitution; Membrane contact sites; Plasma membrane; SMP; Tethering; Tricalbin

DOI: https://doi.org/10.1016/bs.mie.2022.07.003

Curr Genet. 2022 Oct 15.

Peroxisome biogenesis and inter-organelle communication: an indispensable role for Pex11 and Pex30 family proteins in yeast.

Nayan Moni Deori, Shirisha Nagotu.

Peroxisomes are highly dynamic organelles present in most eukaryotic cells. They also play an important role in human health and the optimum functioning of cells. An extensive repertoire of proteins is associated with the biogenesis and function of these organelles. Two protein families that are involved in regulating peroxisome number in a cell directly or indirectly are Pex11 and Pex30. Interestingly, these proteins are also reported to regulate the contact sites between peroxisomes and other cell organelles such as mitochondria, endoplasmic reticulum and lipid droplets. In this manuscript, we review our current knowledge of the role of these proteins in peroxisome biogenesis in various yeast species. Further, we also discuss in detail the role of these protein families in the regulation of inter-organelle contacts in yeast.

Keywords: Contact sites; ER; Peroxisomes; Pex11; Pex30; Yeast

DOI: https://doi.org/10.1007/s00294-022-01254-y

Biochim Biophys Acta Mol Basis Dis. 2022 Oct 11. pii: S0925-4439(22)00241-1. [Epub ahead of print] 166570

Mitoregulin controls mitochondrial function and stress-adaptation response during early phase of endoplasmic reticulum stress in breast cancer cells.

Munkyung Choi, Keon Wook Kang.

The proper regulation of mitochondrial function is important for cellular homeostasis. Especially, in cancer cells, dysregulation of mitochondria is associated with diverse cellular events such as metabolism, redox status, and stress responses. Mitoregulin (MTLN), a micro protein encoded by LINC00116, recently has been reported to control mitochondrial functions in skeletal muscle cells and adipocytes. However, the role of MTLN in cancer cells remains unclear. In the present study, we found that MTLN regulates membrane potential and reactive oxygen species (ROS) generation of mitochondria in breast cancer cells. Moreover, MTLN deficiency resulted in abnormal mitochondria-associated ER membranes (MAMs) formation, which is crucial for stress adaptation. Indeed, the MTLN-deficient breast cancer cells failed to successfully resolve ER (endoplasmic reticulum) stress, and cell vulnerability to ER-stress inducers was significantly enhanced by the downregulation of MTLN. In conclusion, MTLN controls stress-adaptation responses in breast cancer cells as a key regulator of mitochondria-ER harmonization, and thereby its expression level may serve as an indicator of the responsiveness of cancer cells to proteasome inhibitors.

Keywords: ER stress; Mitochondria-associated ER membrane; Mitochondrial quality control; Mitoregulin

DOI: https://doi.org/10.1016/j.bbadis.2022.166570

Neurochem Res. 2022 Oct 12.

2-BFI Provides Neuroprotection Against Fluorosis by Stabilizing Endoplasmic Reticulum-Mitochondria Contact Sites and Inhibiting Activation of the NLRP3 Inflammasome.

Rui Chen, Wan Xu, Yifu Sun, Rongrong Zhi, Peng Xie, Zhongwen Zhi, Xiaohong Tang, Caiyi Zhang.

2-(2-benzofu-ranyl)-2-imidazoline (2-BFI) is a drug that has attracted much attention in recent years. It has a therapeutic effect on brain diseases in animal models such as Alzheimer's disease and cerebral infarction. However, whether 2-BFI affords neuroprotection against the toxicity of fluoride, which can cross the blood-brain barrier and cause neurological dysfunction is not known. We investigated the cell viability and apoptosis of SH-SY5Y cells and primary cultures of cortical neurons exposed to fluoride, and 2-BFI was used to protect both two kinds of cells against the effects of fluoride. We found that 2-BFI can provide neuroprotection on SH-SY5Y cells and primary cultures of cortical neurons upon fluorosis by maintaining the stability of endoplasmic reticulum-mitochondria contact sites and inhibiting activation of the NLR family pyrin domain containing 3 (NLRP3) inflammasome. This study may provide a new method for protecting against the neurotoxicity induced by fluoride exposure.

Keywords: 2-BFI; Endoplasmic reticulum–mitochondria contact sites; NLRP3 inflammasome; NaF; Neuroinflammation

DOI: https://doi.org/10.1007/s11064-022-03781-z

Cell Mol Gastroenterol Hepatol. 2022 Oct 10. pii: S2352-345X(22)00211-9. [Epub ahead of print]

Inhibition of pyruvate dehydrogenase kinase 4 in CD4+ T cells ameliorates intestinal inflammation.

Hoyul Lee, Jae Han Jeon, Yu-Jeong Lee, Mi-Jin Kim, Woong Hee Kwon, Dipanjan Chanda, Themis Thoudam, Haushabhau S Pagire, Suvarna H Pagire, Jin Hee Ahn, Robert A Harris, Eun Soo Kim, In-Kyu Lee.

BACKGROUND AND AIMS: Despite recent evidence supporting the metabolic plasticity of CD4+ T cells, it is uncertain whether the metabolic checkpoint pyruvate dehydrogenase kinase (PDK) in T cells plays a role in the pathogenesis of colitis.
METHODS: To investigate the role of PDK4 in colitis, we used dextran sulfate sodium (DSS)-induced colitis and T cell transfer colitis models based on mice with constitutive knockout (KO) or CD4+ T cell-specific KO of PDK4 (Pdk4fl/flCD4Cre). The effect of PDK4 deletion on T cell activation was also studied in vitro. Furthermore, we examined the effects of a pharmacological inhibitor of PDK4 on colitis.
RESULTS: Expression of PDK4 increased during colitis development in a DSS-induced colitis model. Phosphorylated PDHE1α, a substrate of PDK4, accumulated in CD4+ T cells in the lamina propria of patients with inflammatory bowel disease (IBD). Both constitutive KO and CD4+ T cell-specific deletion of PDK4 delayed DSS-induced colitis. Adoptive transfer of PDK4-deficient CD4+ T cells attenuated murine colitis, and PDK4 deficiency resulted in decreased activation of CD4+ T cells and attenuated aerobic glycolysis. Mechanistically, there were fewer endoplasmic reticulum-mitochondria contact sites, which are responsible for interorganelle calcium transfer, in PDK4-deficient CD4+ T cells. Consistent with this, GM-10395, a novel inhibitor of PDK4, suppressed T cell activation by reducing ER-mitochondria calcium transfer, thereby ameliorating murine colitis.
CONCLUSIONS: PDK4 deletion from CD4+ T cells mitigates colitis by metabolic and calcium signaling modulation, suggesting PDK4 as a potential therapeutic target for IBD.

Keywords: Inflammatory bowel disease; Mitochondria-associated ER membrane; Pyruvate dehydrogenase kinase

DOI: https://doi.org/10.1016/j.jcmgh.2022.09.016