bims-lymeca 2023-07-30 papers

Issue of 2023‒07‒30
six papers selected by
Harilaos Filippakis
University of New England

Proc Natl Acad Sci U S A. 2023 Aug;120(31): e2303789120

LRRK2 suppresses lysosome degradative activity in macrophages and microglia through MiT-TFE transcription factor inhibition.

Narayana Yadavalli, Shawn M Ferguson.

Cells maintain optimal levels of lysosome degradative activity to protect against pathogens, clear waste, and generate nutrients. Here, we show that LRRK2, a protein that is tightly linked to Parkinson's disease, negatively regulates lysosome degradative activity in macrophages and microglia via a transcriptional mechanism. Depletion of LRRK2 and inhibition of LRRK2 kinase activity enhanced lysosomal proteolytic activity and increased the expression of multiple lysosomal hydrolases. Conversely, the kinase hyperactive LRRK2 G2019S Parkinson's disease mutant suppressed lysosomal degradative activity and gene expression. We identified MiT-TFE transcription factors (TFE3, TFEB, and MITF) as mediators of LRRK2-dependent control of lysosomal gene expression. LRRK2 negatively regulated the abundance and nuclear localization of these transcription factors and their depletion prevented LRRK2-dependent changes in lysosome protein levels. These observations define a role for LRRK2 in controlling lysosome degradative activity and support a model wherein LRRK2 hyperactivity may increase Parkinson's disease risk by suppressing lysosome degradative activity.

Keywords: Parkinson’s disease; lysosome; macrophage; microglia

DOI: https://doi.org/10.1073/pnas.2303789120

J Biol Chem. 2023 Jul 26. pii: S0021-9258(23)02125-7. [Epub ahead of print] 105097

Alkaline intracellular pH (pHi) increases PI3K kinase activity to promote mTORC1 and mTORC2 signaling and function during growth factor limitation.

Dubek Kazyken, Stephen I Lentz, Maxwell Wadley, Diane C Fingar.

The conserved protein kinase mTOR (mechanistic target of rapamycin) responds to diverse environmental cues to control cell metabolism and promote cell growth, proliferation, and survival as part of two multiprotein complexes, mTOR complex 1 (mTORC1) and mTORC2. Our prior work demonstrated that an alkaline intracellular pH (pHi) increases mTORC2 activity and cell survival in complete media in part by activating AMPK, a kinase best known to sense energetic stress. It is important to note that an alkaline pHi represents an under-appreciated hallmark of cancer cells that promotes their oncogenic behaviors. In addition, mechanisms that control mTORC1 and mTORC2 signaling and function remain incompletely defined, particularly in response to stress conditions. Here, we demonstrate that an alkaline pHi increases PI3K activity to promote mTORC1 and mTORC2 signaling in the absence of serum growth factors. Alkaline pHi increases mTORC1 activity through PI3K-Akt signaling, which mediates inhibitory phosphorylation of the upstream proteins TSC2 and PRAS40 and dissociates TSC2 from lysosomal membranes, thus enabling Rheb-mediated activation of mTORC1. Thus, we show that an alkaline pHi mimics growth factor-PI3K signaling. Functionally, we also demonstrate that an alkaline pHi increases cap-dependent protein synthesis through inhibitory phosphorylation of 4EBP1 and suppresses apoptosis in a PI3K- and mTOR-dependent manner. We speculate that an alkaline pHi promotes a low, basal level of cell metabolism (e.g., protein synthesis) that enables cancer cells within growing tumors to proliferate and survive despite limiting growth factors and nutrients, in part through elevated PI3K-mTORC1 and/or PI3K-mTORC2 signaling.

Keywords: Akt PKB; S6 kinase; apoptosis; cell signaling; eukaryotic translation initiation factor 4E (eIF4E); eukaryotic translation initiation factor 4E-binding protein (eIF4EBP1); pH regulation; phosphatidylinositide 3-kinase (PI 3-kinase); protein synthesis; target of rapamycin (TOR)

DOI: https://doi.org/10.1016/j.jbc.2023.105097

Pharmaceutics. 2023 Jun 28. pii: 1846. [Epub ahead of print]15(7):

The Exploitation of Lysosomes in Cancer Therapy with Graphene-Based Nanomaterials.

Biljana Ristic, Mihajlo Bosnjak, Maja Misirkic Marjanovic, Danijela Stevanovic, Kristina Janjetovic, Ljubica Harhaji-Trajkovic.

Graphene-based nanomaterials (GNMs), including graphene, graphene oxide, reduced graphene oxide, and graphene quantum dots, may have direct anticancer activity or be used as nanocarriers for antitumor drugs. GNMs usually enter tumor cells by endocytosis and can accumulate in lysosomes. This accumulation prevents drugs bound to GNMs from reaching their targets, suppressing their anticancer effects. A number of chemical modifications are made to GNMs to facilitate the separation of anticancer drugs from GNMs at low lysosomal pH and to enable the lysosomal escape of drugs. Lysosomal escape may be associated with oxidative stress, permeabilization of the unstable membrane of cancer cell lysosomes, release of lysosomal enzymes into the cytoplasm, and cell death. GNMs can prevent or stimulate tumor cell death by inducing protective autophagy or suppressing autolysosomal degradation, respectively. Furthermore, because GNMs prevent bound fluorescent agents from emitting light, their separation in lysosomes may enable tumor cell identification and therapy monitoring. In this review, we explain how the characteristics of the lysosomal microenvironment and the unique features of tumor cell lysosomes can be exploited for GNM-based cancer therapy.

Keywords: cancer; endosomal/lysosomal escape; graphene-based drug delivery systems; graphene-based nanomaterials; lysosomal cell death; lysosomes

DOI: https://doi.org/10.3390/pharmaceutics15071846

Biomedicines. 2023 Jul 20. pii: 2050. [Epub ahead of print]11(7):

The Complex Role of Chaperone-Mediated Autophagy in Cancer Diseases.

Jing Liu, Lijuan Wang, Hua He, Yueying Liu, Yiqun Jiang, Jinfeng Yang.

Chaperone-mediated autophagy (CMA) is a process that rapidly degrades proteins labeled with KFERQ-like motifs within cells via lysosomes to terminate their cellular functioning. Meanwhile, CMA plays an essential role in various biological processes correlated with cell proliferation and apoptosis. Previous studies have shown that CMA was initially found to be procancer in cancer cells, while some theories suggest that it may have an inhibitory effect on the progression of cancer in untransformed cells. Therefore, the complex relationship between CMA and cancer has aroused great interest in the application of CMA activity regulation in cancer therapy. Here, we describe the basic information related to CMA and introduce the physiological functions of CMA, the dual role of CMA in different cancer contexts, and its related research progress. Further study on the mechanism of CMA in tumor development may provide novel insights for tumor therapy targeting CMA. This review aims to summarize and discuss the complex mechanisms of CMA in cancer and related potential strategies for cancer therapy.

Keywords: autophagy; cancer protein; chaperone-mediated; degradation; lysosome

DOI: https://doi.org/10.3390/biomedicines11072050

Pharmaceuticals (Basel). 2023 Jul 14. pii: 1004. [Epub ahead of print]16(7):

Exploring the mTOR Signalling Pathway and Its Inhibitory Scope in Cancer.

Suhail Ahmad Mir, Ashraf Dar, Saad Ali Alshehri, Shadma Wahab, Laraibah Hamid, Mohammad Ali Abdullah Almoyad, Tabasum Ali, Ghulam Nabi Bader.

Mechanistic target of rapamycin (mTOR) is a protein kinase that regulates cellular growth, development, survival, and metabolism through integration of diverse extracellular and intracellular stimuli. Additionally, mTOR is involved in interplay of signalling pathways that regulate apoptosis and autophagy. In cells, mTOR is assembled into two complexes, mTORC1 and mTORC2. While mTORC1 is regulated by energy consumption, protein intake, mechanical stimuli, and growth factors, mTORC2 is regulated by insulin-like growth factor-1 receptor (IGF-1R), and epidermal growth factor receptor (EGFR). mTOR signalling pathways are considered the hallmark in cancer due to their dysregulation in approximately 70% of cancers. Through downstream regulators, ribosomal protein S6 kinase β-1 (S6K1) and eukaryotic translation initiation factor 4E binding protein 1 (4E-BP1), mTORC1 influences various anabolic and catabolic processes in the cell. In recent years, several mTOR inhibitors have been developed with the aim of treating different cancers. In this review, we will explore the current developments in the mTOR signalling pathway and its importance for being targeted by various inhibitors in anti-cancer therapeutics.

Keywords: cancer; mTOR inhibitors; mTORC1/2; rapamycin; regulation of mTOR signalling pathway

DOI: https://doi.org/10.3390/ph16071004

Nature. 2023 Jul 26.

Rewiring cancer drivers to activate apoptosis.

Sai Gourisankar, Andrey Krokhotin, Wenzhi Ji, Xiaofan Liu, Chiung-Ying Chang, Samuel H Kim, Zhengnian Li, Wendy Wenderski, Juste M Simanauskaite, Haopeng Yang, Hannes Vogel, Tinghu Zhang, Michael R Green, Nathanael S Gray, Gerald R Crabtree.

Genes that drive the proliferation, survival, invasion and metastasis of malignant cells have been identified for many human cancers1-4. Independent studies have identified cell death pathways that eliminate cells for the good of the organism5,6. The coexistence of cell death pathways with driver mutations suggests that the cancer driver could be rewired to activate cell death using chemical inducers of proximity (CIPs). Here we describe a new class of molecules called transcriptional/epigenetic CIPs (TCIPs) that recruit the endogenous cancer driver, or a downstream transcription factor, to the promoters of cell death genes, thereby activating their expression. We focused on diffuse large B cell lymphoma, in which the transcription factor B cell lymphoma 6 (BCL6) is deregulated7. BCL6 binds to the promoters of cell death genes and epigenetically suppresses their expression8. We produced TCIPs by covalently linking small molecules that bind BCL6 to those that bind to transcriptional activators that contribute to the oncogenic program, such as BRD4. The most potent molecule, TCIP1, increases binding of BRD4 by 50% over genomic BCL6-binding sites to produce transcriptional elongation at pro-apoptotic target genes within 15 min, while reducing binding of BRD4 over enhancers by only 10%, reflecting a gain-of-function mechanism. TCIP1 kills diffuse large B cell lymphoma cell lines, including chemotherapy-resistant, TP53-mutant lines, at EC50 of 1-10 nM in 72 h and exhibits cell-specific and tissue-specific effects, capturing the combinatorial specificity inherent to transcription. The TCIP concept also has therapeutic applications in regulating the expression of genes for regenerative medicine and developmental disorders.

DOI: https://doi.org/10.1038/s41586-023-06348-2