scholarly journals Mitochondrial division, fusion and degradation

2019 ◽  
Vol 167 (3) ◽  
pp. 233-241 ◽  
Author(s):  
Daisuke Murata ◽  
Kenta Arai ◽  
Miho Iijima ◽  
Hiromi Sesaki
Keyword(s):  
Super Resolution ◽  
Healthy Population ◽  
Lipid Biochemistry ◽  
Mitochondrial Division ◽  
Cellular Processes ◽  
Size Number ◽  
Wide Range ◽  
Autophagic Degradation ◽  
And Function

Abstract The mitochondrion is an essential organelle for a wide range of cellular processes, including energy production, metabolism, signal transduction and cell death. To execute these functions, mitochondria regulate their size, number, morphology and distribution in cells via mitochondrial division and fusion. In addition, mitochondrial division and fusion control the autophagic degradation of dysfunctional mitochondria to maintain a healthy population. Defects in these dynamic membrane processes are linked to many human diseases that include metabolic syndrome, myopathy and neurodegenerative disorders. In the last several years, our fundamental understanding of mitochondrial fusion, division and degradation has been significantly advanced by high resolution structural analyses, protein-lipid biochemistry, super resolution microscopy and in vivo analyses using animal models. Here, we summarize and discuss this exciting recent progress in the mechanism and function of mitochondrial division and fusion.

scholarly journals Cooperative subunit dynamics modulate p97 function

2018 ◽  
Vol 116 (1) ◽  
pp. 158-167 ◽  
Author(s):  
Rui Huang ◽  
Zev A. Ripstein ◽  
John L. Rubinstein ◽  
Lewis E. Kay
Keyword(s):  
Bound State ◽  
Nmr Studies ◽  
Biologically Relevant ◽  
Aaa Atpase ◽  
Cellular Processes ◽  
Allosteric Communication ◽  
Functional Dynamics ◽  
Nmr Study ◽  
Wide Range

p97 is an essential hexameric AAA+ ATPase involved in a wide range of cellular processes. Mutations in the enzyme are implicated in the etiology of an autosomal dominant neurological disease in which patients are heterozygous with respect to p97 alleles, containing one copy each of WT and disease-causing mutant genes, so that, in vivo, p97 molecules can be heterogeneous in subunit composition. Studies of p97 have, however, focused on homohexameric constructs, where protomers are either entirely WT or contain a disease-causing mutation, showing that for WT p97, the N-terminal domain (NTD) of each subunit can exist in either a down (ADP) or up (ATP) conformation. NMR studies establish that, in the ADP-bound state, the up/down NTD equilibrium shifts progressively toward the up conformation as a function of disease mutant severity. To understand NTD functional dynamics in biologically relevant p97 heterohexamers comprising both WT and disease-causing mutant subunits, we performed a methyl-transverse relaxation optimized spectroscopy (TROSY) NMR study on a series of constructs in which only one of the protomer types is NMR-labeled. Our results show positive cooperativity of NTD up/down equilibria between neighboring protomers, allowing us to define interprotomer pathways that mediate the allosteric communication between subunits. Notably, the perturbed up/down NTD equilibrium in mutant subunits is partially restored by neighboring WT protomers, as is the two-pronged binding of the UBXD1 adaptor that is affected in disease. This work highlights the plasticity of p97 and how subtle perturbations to its free-energy landscape lead to significant changes in NTD conformation and adaptor binding.

scholarly journals hPSC-Derived Enteric Ganglioids Model Human ENS Development and Function

2022 ◽  
Author(s):  
Homa Majd ◽  
Ryan M Samuel ◽  
Jonathan T Ramirez ◽  
Ali Kalantari ◽  
Kevin Barber ◽  
...  
Keyword(s):  
Ex Vivo ◽  
Xenograft Model ◽  
Developmental Relationships ◽  
Drug Candidates ◽  
Effective Strategies ◽  
Wide Range ◽  
Functional Features ◽  
And Function

The enteric nervous system (ENS) plays a central role in gut physiology and mediating the crosstalk between the gastrointestinal (GI) tract and other organs. The human ENS has remained elusive, highlighting the need for an in vitro modeling and mapping blueprint. Here we map out the developmental and functional features of the human ENS, by establishing robust and scalable 2D ENS cultures and 3D enteric ganglioids from human pluripotent stem cells (hPSCs). These models recapitulate the remarkable neuronal and glial diversity found in primary tissue and enable comprehensive molecular analyses that uncover functional and developmental relationships within these lineages. As a salient example of the power of this system, we performed in-depth characterization of enteric nitrergic neurons (NO neurons) which are implicated in a wide range of GI motility disorders. We conducted an unbiased screen and identified drug candidates that modulate the activity of NO neurons and demonstrated their potential in promoting motility in mouse colonic tissue ex vivo. We established a high-throughput strategy to define the developmental programs involved in NO neuron specification and discovered that PDGFR inhibition boosts the induction of NO neurons in enteric ganglioids. Transplantation of these ganglioids in the colon of NO neuron-deficient mice results in extensive tissue engraftment, providing a xenograft model for the study of human ENS in vivo and the development of cell-based therapies for neurodegenerative GI disorders. These studies provide a framework for deciphering fundamental features of the human ENS and designing effective strategies to treat enteric neuropathies.  

scholarly journals Dnm1 forms spirals that are structurally tailored to fit mitochondria

2005 ◽  
Vol 170 (7) ◽  
pp. 1021-1027 ◽  
Author(s):  
Elena Ingerman ◽  
Edward M. Perkins ◽  
Michael Marino ◽  
Jason A. Mears ◽  
J. Michael McCaffery ◽  
...  
Keyword(s):  
Self Assembly ◽  
Membrane Dynamics ◽  
Nucleotide Hydrolysis ◽  
Mitochondrial Division ◽  
Cellular Processes ◽  
Self Assembling ◽  
Related Proteins ◽  
Rate Limiting ◽  
Common Function

Dynamin-related proteins (DRPs) are large self-assembling GTPases whose common function is to regulate membrane dynamics in a variety of cellular processes. Dnm1, which is a yeast DRP (Drp1/Dlp1 in humans), is required for mitochondrial division, but its mechanism is unknown. We provide evidence that Dnm1 likely functions through self-assembly to drive the membrane constriction event that is associated with mitochondrial division. Two regulatory features of Dnm1 self-assembly were also identified. Dnm1 self-assembly proceeded through a rate-limiting nucleation step, and nucleotide hydrolysis by assembled Dnm1 structures was highly cooperative with respect to GTP. Dnm1 formed extended spirals, which possessed diameters greater than those of dynamin-1 spirals but whose sizes, remarkably, were equal to those of mitochondrial constriction sites in vivo. These data suggest that Dnm1 has evolved to form structures that fit the dimensions of mitochondria.

CAN COMPLEX CELLULAR PROCESSES BE GOVERNED BY SIMPLE LINEAR RULES?

2009 ◽  
Vol 07 (01) ◽  
pp. 243-268 ◽  
Author(s):  
KUMAR SELVARAJOO ◽  
MASARU TOMITA ◽  
MASA TSUCHIYA
Keyword(s):  
Biological Networks ◽  
Biological Network ◽  
Living Systems ◽  
Regulatory Motifs ◽  
Cellular Processes ◽  
Self Organized ◽  
Wide Range ◽  
Activation Response ◽  
Physical Reasons

Complex living systems have shown remarkably well-orchestrated, self-organized, robust, and stable behavior under a wide range of perturbations. However, despite the recent generation of high-throughput experimental datasets, basic cellular processes such as division, differentiation, and apoptosis still remain elusive. One of the key reasons is the lack of understanding of the governing principles of complex living systems. Here, we have reviewed the success of perturbation–response approaches, where without the requirement of detailed in vivo physiological parameters, the analysis of temporal concentration or activation response unravels biological network features such as causal relationships of reactant species, regulatory motifs, etc. Our review shows that simple linear rules govern the response behavior of biological networks in an ensemble of cells. It is daunting to know why such simplicity could hold in a complex heterogeneous environment. Provided physical reasons can be explained for these phenomena, major advancement in the understanding of basic cellular processes could be achieved.

scholarly journals Ligand Geometry Controls Adhesion formation via Integrin Clustering

2018 ◽  
Author(s):  
Rishita Changede ◽  
Haogang Cai ◽  
Shalom Wind ◽  
Michael P. Sheetz
Keyword(s):  
Adhesion Formation ◽  
Focal Adhesions ◽  
Super Resolution ◽  
Total Width ◽  
Cellular Processes ◽  
Cell Matrix ◽  
Integrin Clustering ◽  
Super Resolution Microscopy ◽  
Fiber Mesh

AbstractIntegrin-mediated cell matrix adhesions are key to sensing the geometry and rigidity of the extracellular environment to regulate vital cellular processes. In vivo, the extracellular matrix (ECM) is composed of a fibrous mesh. To understand the geometry that supports adhesion formation on fibrous substrates, we patterned 10 nm gold-palladium single lines or pairs of lines (total width within 100 nm), mimicking thin single ECM fibers or a minimal mesh geometry, respectively and functionalized it with integrin binding ligand Arg-Gly-Asp (RGD). Single lines showed reduced focal adhesion kinase (FAK) recruitment and did not support cell spreading or formation of focal adhesions, despite the presence of a high density of integrin-binding ligands. Using super resolution microscopy, we observed transient integrin clusters on single lines, whereas stable 110 nm integrin clusters formed on pairs of lines similar to those on continuous substrates. This indicated that two-dimensional ligand geometry is required for adhesion formation on rigid substrates. A mechanism to form modular 100nm integrin clusters bridging the minimal fiber mesh would require unliganded integrins. We observed that integrin mutants unable to bind ligand co-clustered with ligand-bound integrins when present in an active extended conformation. Thus, these results indicate that functional integrin clusters are required to form focal adhesions and unliganded integrins can co-cluster to bridge between thin matrix fibers and can form stable integrin adhesions on dense fibrous networks.

scholarly journals Role of Exosomes in Islet Transplantation

2021 ◽  
Vol 12 ◽  
Author(s):  
Jordan Mattke ◽  
Srividya Vasu ◽  
Carly M. Darden ◽  
Kenjiro Kumano ◽  
Michael C. Lawrence ◽  
...  
Keyword(s):  
Islet Transplantation ◽  
Graft Function ◽  
Pancreatic Islet Transplantation ◽  
Complex Molecules ◽  
Wide Range ◽  
And Function ◽  
Antigen Presenting

Exosomes are known for their ability to transport nucleic acid, lipid, and protein molecules, which allows for communication between cells and tissues. The cargo of the exosomes can have a variety of effects on a wide range of targets to mediate biological function. Pancreatic islet transplantation is a minimally invasive cell replacement therapy to prevent or reverse diabetes mellitus and is currently performed in patients with uncontrolled type 1 diabetes or chronic pancreatitis. Exosomes have become a focus in the field of islet transplantation for the study of diagnostic markers of islet cell viability and function. A growing list of miRNAs identified from exosomes collected during the process of isolating islets can be used as diagnostic biomarkers of islet stress and damage, leading to a better understanding of critical steps of the isolation procedure that can be improved to increase islet yield and quality. Exosomes have also been implicated as a possible contributor to islet graft rejection following transplantation, as they carry donor major histocompatibility complex molecules, which are then processed by recipient antigen-presenting cells and sensed by the recipient immune cells. Exosomes may find their way into the therapeutic realm of islet transplantation, as exosomes isolated from mesenchymal stem cells have shown promising results in early studies that have seen increased viability and functionality of isolated and grafted islets in vitro as well as in vivo. With the study of exosomes still in its infancy, continued research on the role of exosomes in islet transplantation will be paramount to understanding beta cell regeneration and improving long-term graft function.

scholarly journals Dihydroceramide desaturase directs the switch between exosome production and autophagy for neuronal maintenance

2020 ◽  
Author(s):  
Chen-Yi Wu ◽  
Jhih-Gang Jhang ◽  
Chih-Wei Lin ◽  
Han-Chen Ho ◽  
Chih-Chiang Chan ◽  
...  
Keyword(s):  
Nervous System ◽  
Desaturase Gene ◽  
Dihydroceramide Desaturase ◽  
Autophagic Degradation ◽  
Photoreceptor Neurons ◽  
And Function ◽  
Neuronal Maintenance ◽  
Autophagy Inhibition

ABSTRACTExosomes play important roles in the nervous system. Mutations in the human dihydroceramide desaturase gene, DEGS1, are recently linked to severe neurological disorders, but the cause remains unknown. Here, we show that Ifc is required for the morphology and function of Drosophila photoreceptor neurons and not in the surrounding glia, but the degeneration of ifc-KO eyes can be rescued by glial expression of ifc, possibly mediated by exosomes. We develop an in vivo assay using Drosophila eye imaginal discs and show that the level and activity of Ifc correlates with the detection of exosome-like vesicles. While ifc overexpression and autophagy inhibition both enhances exosome production, combining the two had no additive effect. Moreover, ifc-KO reduces the density of the exosome precursor intraluminal vesicles (ILVs) in vivo, and DEGS1 promotes ILV formation in vitro. In conclusion, dihydroceramide desaturase promotes exosome formation and prevents its autophagic degradation in the nervous system.

scholarly journals Protein manipulation using single copies of short peptide tags in cultured cells and in Drosophila melanogaster

2020 ◽  
Author(s):  
M. Alessandra Vigano ◽  
Clara-Maria Ell ◽  
Manuela MM Kustermann ◽  
Gustavo Aguilar ◽  
Shinya Matsuda ◽  
...  
Keyword(s):  
Cultured Cells ◽  
Single Copy ◽  
Specific Protein ◽  
Cellular Functions ◽  
Cellular Processes ◽  
Peptide Tags ◽  
Genetic Technologies ◽  
Protein Binders ◽  
And Function

AbstractCellular development and specialized cellular functions are regulated processes which rely on highly dynamic molecular interactions among proteins, distributed in all cell compartments. Analysis of these interactions and their mechanisms of action has been one of the main topics in cellular and developmental research over the last fifty years. Studying and understanding the functions of proteins of interest (POIs) has been mostly achieved by their alteration at the genetic level and the analysis of the phenotypic changes generated by these alterations. Although genetic and reverse genetic technologies contributed to the vast majority of information and knowledge we have gathered so far, targeting specific interactions of POIs in a time- and space-controlled manner or analyzing the role of POIs in dynamic cellular processes such as cell migration or cell division would require more direct approaches. The recent development of specific protein binders, which can be expressed and function intracellularly, together with several improvements in synthetic biology techniques, have contributed to the creation of a new toolbox for direct protein manipulations. We selected a number of short tag epitopes for which protein binders from different scaffolds have been developed and tested whether these tags can be bound by the corresponding protein binders in living cells when they are inserted in a single copy in a POI. We indeed find that in all cases, a single copy of a short tag allows protein binding and manipulation. Using Drosophila, we also find that single short tags can be recognized and allow degradation and relocalization of POIs in vivo.

scholarly journals Protein manipulation using single copies of short peptide tags in cultured cells and in Drosophila melanogaster

Development ◽  
2021 ◽  
Vol 148 (6) ◽  
Author(s):  
M. Alessandra Vigano ◽  
Clara-Maria Ell ◽  
Manuela M. M. Kustermann ◽  
Gustavo Aguilar ◽  
Shinya Matsuda ◽  
...  
Keyword(s):  
Cultured Cells ◽  
Specific Protein ◽  
Cellular Processes ◽  
Cell Compartments ◽  
Peptide Tags ◽  
Genetic Level ◽  
Protein Binders ◽  
And Function

ABSTRACT Cellular development and function rely on highly dynamic molecular interactions among proteins distributed in all cell compartments. Analysis of these interactions has been one of the main topics in cellular and developmental research, and has been mostly achieved by the manipulation of proteins of interest (POIs) at the genetic level. Although genetic strategies have significantly contributed to our current understanding, targeting specific interactions of POIs in a time- and space-controlled manner or analysing the role of POIs in dynamic cellular processes, such as cell migration or cell division, would benefit from more-direct approaches. The recent development of specific protein binders, which can be expressed and function intracellularly, along with advancement in synthetic biology, have contributed to the creation of a new toolbox for direct protein manipulations. Here, we have selected a number of short-tag epitopes for which protein binders from different scaffolds have been generated and showed that single copies of these tags allowed efficient POI binding and manipulation in living cells. Using Drosophila, we also find that single short tags can be used for POI manipulation in vivo.

scholarly journals Laminin-521 Protein Therapy for Glomerular Basement Membrane and Podocyte Abnormalities in a Model of Pierson Syndrome

2018 ◽  
Vol 29 (5) ◽  
pp. 1426-1436 ◽  
Author(s):  
Meei-Hua Lin ◽  
Joseph B. Miller ◽  
Yamato Kikkawa ◽  
Hani Y. Suleiman ◽  
Karl Tryggvason ◽  
...  
Keyword(s):  
Nephrotic Syndrome ◽  
Congenital Nephrotic Syndrome ◽  
Super Resolution ◽  
Diffuse Mesangial Sclerosis ◽  
Protein Therapy ◽  
Correct Orientation ◽  
Pierson Syndrome ◽  
Foot Process ◽  
And Function

Background Laminin α5β2γ1 (LM-521) is a major component of the GBM. Mutations in LAMB2 that prevent LM-521 synthesis and/or secretion cause Pierson syndrome, a rare congenital nephrotic syndrome with diffuse mesangial sclerosis and ocular and neurologic defects. Because the GBM is uniquely accessible to plasma, which permeates endothelial cell fenestrae, we hypothesized that intravenous delivery of LM-521 could replace the missing LM-521 in the GBM of Lamb2 mutant mice and restore glomerular permselectivity.Methods We injected human LM-521 (hLM-521), a macromolecule of approximately 800 kD, into the retro-orbital sinus of Lamb2−/− pups daily. Deposition of hLM-521 into the GBM was investigated by fluorescence microscopy. We assayed the effects of hLM-521 on glomerular permselectivity by urinalysis and the effects on podocytes by desmin immunostaining and ultrastructural analysis of podocyte architecture.Results Injected hLM-521 rapidly and stably accumulated in the GBM of all glomeruli. Super-resolution imaging showed that hLM-521 accumulated in the correct orientation in the GBM, primarily on the endothelial aspect. Treatment with hLM-521 greatly reduced the expression of the podocyte injury marker desmin and attenuated the foot process effacement observed in untreated pups. Moreover, treatment with hLM-521 delayed the onset of proteinuria but did not prevent nephrotic syndrome, perhaps due to its absence from the podocyte aspect of the GBM.Conclusions These studies show that GBM composition and function can be altered in vivovia vascular delivery of even very large proteins, which may advance therapeutic options for patients with abnormal GBM composition, whether genetic or acquired.

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