Biology subjects

Tsutsumi, R.

Publications and source records attributed to Tsutsumi, R..

9 recordsLinked to original sources

bioRxiv2026

Endocytosis of ALK promotes glucose uptake in ALK-amplified neuroblastoma

Activated receptor tyrosine kinases (RTKs), such as epidermal growth factor receptor (EGFR) and anaplastic lymphoma kinase (ALK), trigger intracellular signaling while undergoing receptor endocytosis. We recently identified a noncanonical mechanism in which RTK-containing endocytic vesicles deliver extracellular glucose to hexokinases associated with the outer mitochondrial membrane, thereby promoting cellular glucose uptake. Whether this mechanism contributes to cancer metabolism, however, remains unknown. Here, using neuroblastoma cell lines with distinct ALK alterations, we investigated the role of ALK endocytosis in glucose uptake. ALK-amplified, but not ALK-mutant, neuroblastoma cells exhibited a [~]40- 50% reduction in glucose uptake following inhibition of ALK or receptor endocytosis. This process was independent of the ERK MAPK and PI3K-AKT pathways but required dynamin-dependent endocytosis, cytoplasmic dynein, and GLUT1. Overexpressed ALK constitutively co-endocytosed with GLUT1 into vesicles transported to mitochondria. Inhibition of ALK activity or endocytosis suppressed glucose uptake without producing an additive effect, indicating that both function within the same pathway. Furthermore, disruption of the endocytic machinery selectively impaired the growth of ALK-amplified neuroblastoma cells. These findings identify ALK endocytosis as a major regulator of glucose uptake in ALK-amplified neuroblastoma and suggest that RTK endocytosis represents a previously unrecognized metabolic vulnerability that may be therapeutically exploitable in RTK-driven cancers.

cancer biology↗

bioRxiv2025

Self-organized fingering instabilities drive the emergence of tissue morphogenesis in digit organoids.

The emergence of complex anatomical structures -such as the hands- from unstructured tissues remains a fundamental question in developmental biology. Turing-type reaction-diffusion models have provided a molecular explanation for the periodic pre-patterning of digits; however, the physical principles driving 3D morphogenesis remain incompletely understood. To identify the biophysical design principles leading to digit formation, we develop a limb-mesenchymal organoid system that spontaneously forms elongated, digit-like protrusions. Iterations between experiments and agent-based models at the cellular level identify sufficient microscopic mechanisms leading to morphogenesis of digit-like structures: symmetry-breaking and the elongation of digits result from a combination of differential cell adhesion and morphogen-induced chemotaxis and convergent-extension. Lastly, to describe tissue-scale deformations, we perform a coarse-graining analysis of the agent-based model and derive a continuum model that reveals a structural analogy to Cahn-Hilliard-type equations. These equations are typically used to describe fluid phase separation and so-called ''fingering instabilities'' in fluid physics. Here, we show that they also accurately describe organoid morphogenesis. These findings suggest that ''finger'' formation is driven by a mechanical fingering instability acting in concert with chemical patterning, shedding a new light on vertebrate limb morphogenesis.

developmental biology↗

bioRxiv2024

Ccrk-Mak/Ick kinase signaling axis is a ciliary transport regulator essential for retinal photoreceptor maintenance

Primary cilia are microtubule-based sensory organelles whose dysfunction leads to ciliopathies in humans. The formation, function, and maintenance of primary cilia depend crucially on intraflagellar transport (IFT); however, the regulatory mechanisms of IFT and their physiological roles are poorly understood. In the current study, we screened and identified that the ciliopathy kinase Mak is a ciliary tip-localized IFT regulator that cooperatively acts with the ciliopathy kinase Ick, an IFT regulator. Simultaneous disruption of Mak and Ick resulted in loss of photoreceptor ciliary axonemes and severe degeneration in the mouse retina. Mak overexpression restored ciliary defects caused by Ick deficiency in cultured cells. Gene delivery of Ick and pharmacological inhibition of FGF receptors, negative regulators of Ick, ameliorated retinal degeneration in Mak-/-mice. In addition, we identified that Ccrk kinase is an upstream activator of Mak and Ick in retinal photoreceptor cells. Furthermore, overexpression of Mak, Ick, and Ccrk and pharmacological inhibition of FGF receptors suppressed ciliopathy-related phenotypes caused by cytoplasmic dynein inhibition in cultured cells. Collectively, our results show that the Ccrk-Mak/Ick axis is an essential IFT regulator crucial for retinal photoreceptor maintenance. This study sheds light on pathological mechanisms underlying retinitis pigmentosa caused by mutations in the human MAK gene and presents activation of Ick as a potential therapeutic approach for this retinal degenerative disease.

developmental biology↗

bioRxiv2024

Brown Adipose Tissue and Skeletal Muscle Coordinately Contribute to Thermogenesis in Mice

Endotherms increase the rate of metabolism in metabolic organs as one strategy to cope with a decline in temperature of the external environment. However, an additional major contributor to maintenance of body temperature in a cold environment is contraction-based thermogenesis in skeletal muscle. Here, we show that impairment of hind limb muscle contraction by cast immobilization induced a loss of function of skeletal muscle and activated brown adipose tissue (BAT) thermogenesis as a compensatory mechanism. BAT utilizes free branched-chain amino acids (BCAAs) derived from skeletal muscle as an energy substrate for thermogenesis, and interleukin-6 released by skeletal muscle stimulates BCAAs production in muscle for support of BAT thermogenesis. Additionally, this thermoregulatory system between BAT and skeletal muscle may also play an important role in response to cold temperatures or acute stress. Our findings suggest that BAT and skeletal muscle cooperate to maintain body temperature in endotherms.

molecular biology↗

bioRxiv2023

Endocytic vesicles act as vehicles for glucose uptake in response to growth factor stimulation

Glycolysis is a fundamental cellular process, yet its regulatory mechanisms remain incompletely understood. Here, we show that a subset of glucose transporter 1 (GLUT1/SLC2A1) co-endocytoses with platelet-derived growth factor (PDGF) receptor (PDGFR) upon PDGF-stimulation. Furthermore, multiple glycolytic enzymes localize to these endocytosed PDGFR/GLUT1-containing vesicles adjacent to mitochondria. Contrary to current models, which emphasize the importance of glucose transporters on the cell surface, we find that PDGF-stimulated glucose uptake depends on receptor/transporter endocytosis. Our results suggest that growth factors generate glucose-loaded endocytic vesicles that deliver glucose to the glycolytic machinery in proximity to mitochondria, and argue for a new layer of regulation for glycolytic control governed by cellular membrane dynamics.

cell biology↗

bioRxiv2019

Convergent metatarsal fusion in jerboas and chickens is mediated by similarities and differences in the patterns of osteoblast and osteoclast activities

The extraordinary malleability of the vertebrate limb supports a variety of locomotor functions including running and leaping in cursorial and saltatorial species. In many of these animals, the metatarsals and/or metacarpals are disproportionately elongated to increase stride length and fused into a single larger element, likely to resist fracture due to increased ground reaction forces. Despite the fact that metapodial fusion evolved convergently in modern birds, ungulates, and jerboas, the developmental basis has only been explored in chickens, which diverged from the mammalian lineage approximately 300 million years ago. Here, we use the lesser Egyptian jerboa, Jaculus jaculus, to understand the cellular processes that unite three distinct metatarsal elements into a single cannon bone in a mammal, and we revisit the developing chicken to assess similarities and differences in the localization of osteoblast and osteoclast activities. In both species, adjacent metatarsals align along flat surfaces, osteoblasts cross the periosteal membrane to unite the three elements in a single circumference, and osteoclasts resorb bone at the interfaces leaving a single marrow cavity. However, although spatial and temporal partitioning of osteoblast and osteoclast activities reshape three bones into one in both species, the localization of osteoclasts is distinct. While osteoclasts are uniformly distributed throughout the endosteum of chicken metatarsals, these catabolic cells are highly localized to resorb bone at the interfaces of neighboring jerboa metatarsals. Each species therefore provides an opportunity to better understand the mechanisms that partition osteoblasts and osteoclasts to alter the shape of bone during development and evolution.

evolutionary biology↗

bioRxiv2019

Evolutionary loss of foot muscle during development with characteristics of atrophy and no evidence of cell death

Many species that run or leap across sparsely vegetated habitats, including horses and deer, evolved the severe reduction or complete loss of foot muscles as skeletal elements elongated and digits were lost, and yet the developmental mechanisms remain unknown. Here, we report the natural loss of foot muscles in the bipedal jerboa, Jaculus jaculus. Although adults have no muscles in their feet, newborn animals have muscles that rapidly disappear soon after birth. We were surprised to find no evidence of apoptotic or necrotic cell death during stages of peak myofiber loss, countering well-supported assumptions of developmental tissue remodeling. We instead see hallmarks of muscle atrophy, including an ordered disassembly of the sarcomere associated with upregulation of the E3 ubiquitin ligases, MuRF1 and Atrogin-1. We propose that the natural loss of muscle, which remodeled foot anatomy during evolution and development, involves cellular mechanisms that are typically associated with disease or injury.

developmental biology↗

bioRxiv2018

Off-target inhibition by active site-targeting SHP2 inhibitors

Due to the involvement of SHP2 (SH2 domain-containing protein tyrosine phosphatase) in human disease, including Noonan syndrome and cancer, several inhibitors targeting SHP2 have been developed. Here, we report that the commonly used SHP2 inhibitor NSC-78788 does not exhibit robust inhibitory effects on growth factor-dependent MAPK (mitogen-activated protein kinase) pathway activation, and that the recently developed active site-targeting SHP2 inhibitors IIB-08, 11a-1, and GS-493 show off-target effects on ligand-evoked activation/trans-phosphorylation of the PDGFR{beta} (platelet-derived growth factor receptor {beta}). GS-493 also inhibits purified human PDGFR{beta} and SRC in vitro, whereas PDGFR{beta} inhibition by IIB-08 and 11a-1 occurs only in the cellular context. Our results argue for extreme caution in inferring specific functions for SHP2 based on studies using these inhibitors.

cell biology↗

bioRxiv2017

Assay to visualize specific protein oxidation reveals spatio-temporal regulation of SHP2

Reactive oxygen species (ROS) are produced transiently in response to cell stimuli, and function as second messengers that oxidize target proteins. Protein-tyrosine phosphatases (PTPs) are important ROS targets, whose oxidation results in rapid, reversible, catalytic inactivation. Despite increasing evidence for the importance of PTP oxidation in signal transduction, the cell biological details of ROS-catalyzed PTP inactivation have remained largely unclear, due to our inability to visualize PTP oxidation in cells. By combining proximity ligation assay (PLA) with chemical labeling of cysteine residues in the sulfenic acid state, we visualize oxidized Src homology 2 domain-containing protein-tyrosine phosphatase 2 (SHP2). We find that platelet-derived growth factor (PDGF) evokes transient oxidation on or close to RAB5+/EEA1-endosomes. SHP2 oxidation requires NADPH oxidases (NOXs), and oxidized SHP2 co-localizes with PDGF receptor and NOX1/4. Our data demonstrate spatially and temporally limited protein oxidation within cells, and suggest that PDGF-dependent \"redoxosomes,\" contribute to proper signal transduction.

cell biology↗