Effects of Actin-Binding Proteins - Tropomodulins and Tropomyosins, on Dynamics of Actin Filaments in Non-muscle Cells

Effects of Actin-Binding Proteins - Tropomodulins and Tropomyosins, on Dynamics of Actin Filaments in Non-muscle Cells
Author: Balaganesh Kuruba
Publisher:
Total Pages: 0
Release: 2023
Genre: Microfilament proteins
ISBN:

The ability of the brain to adapt to environmental or activity-dependent changes is regarded as synaptic plasticity. Synaptic communication occurs between presynaptic terminal (axon) and post synaptic terminal, which in a neuron is an actin-rich protrusion arising from dendrites called spines. Dendritic spines are highly dynamic structures and the synaptic input dependent regulation of their morphology correlates to structural synaptic plasticity. Systematic modulation of cytoskeletal actin by numerous actin binding and regulating proteins, is essential for spine morphogenesis, maturation, stabilization, and organization. Cytoskeletal actin is composed of monomeric G-actin. This monomeric G-actin polymerizes to form polymeric filamentous actin (F-actin) in various forms such as linear, bundled, branched, mesh, etc. Actin filaments are highly dynamic structures with a slow growing (pointed) end and a fast growing (barbed) end. The kinetics of F-actin depolymerization at the pointed end serves as the rate limiting step for maintaining the cytoplasmic pool of G actin for filament assembly. Regulation of F-actin length and dynamics by the pointed end binding proteins still needs to be fully understood, especially in non-muscle cells. Due to the structural complexities posed by the pointed-end binding proteins - tropomodulin (Tmod) and tropomyosin (Tpm) - there is a lack of 3D structural information which is essential to understand the mechanism of the pointed end regulation. Very few studies have been conducted on the role of pointed-end binding proteins in regulation of dendritic spine morphology.In this dissertation, the work presented focuses on highlighting the role played by tropomodulin 2 (Tmod2), a brain-specific isoform, on the dendritic spine re-organization. Tmod2 regulates actin-polymerization by binding to the F-actin pointed end with its distinct actin and tropomyosin (Tpm) binding sites. To provide better understanding of the pointed end regulation by Tpm and Tmod, we engineered Tpm fragments that were used to obtain structural information regarding Tpm-Tmod interface at the pointed end. We provided the structural basis for this interface using circular dichroism (CD), nuclear magnetic resonance (NMR) spectroscopic techniques and molecular dynamic simulations (MDS) to map the region of Tpm-Tmod interactions. We further investigated the effects of overexpressing Tmod2 on the morphological reorganization of dendritic spines and other actin-based structures, after they were formed. We provided information that illuminated the effects that Tmod2 overexpression had on numbers of thin, mushroom, and stubby spines, and other actin-based structures - branched spines, excitatory shaft synapses, dendritic filopodia and spinules. We also provided data on the effects Tmod2 had on dendritic spine motility. We show that Tpm-binding and actin-binding abilities of Tmod2 have distinct roles in spine reorganization, thus accentuating the role of pointed end regulation in dendritic spine related structural synaptic plasticity.

Tropomyosin

Tropomyosin
Author: Peter Gunning
Publisher: Springer Science & Business Media
Total Pages: 323
Release: 2009-09-30
Genre: Medical
ISBN: 0387857664

A recent review of one of my grant applications commented on the ‘rediscovery of tropomyosin’. I was tempted to write back in my rebuttal to the reviewer that I didn’t realise it had been lost. Uncharacteristic maturity prevailed and I resisted the temptation, but I was struck by the underlying observation that research on the str- ture and function of tropomyosin has been somewhat invisible, particularly in terms of the cytoskeleton isoforms. So, how can it be that one of the two major components of the actin filament has been so thoroughly overlooked? I suspect that the answer is disappointingly pedestrian. Whereas the biochemistry of the 1980s revealed the potential of tropomyosin isoforms to diversify the function of actin filaments, the subsequent disenchantment with isoform biology in general in the 1990s inhibited growth of this field. With the development of more sophisticated experimental - proaches we are now seeing a growing realisation of the importance of tropomyosin in regulating actin filaments beyond its pivotal role in muscle contraction. The opportunity to edit this book came at a time when we had written several reviews on different aspects of tropomyosin function and I had just finished the background reading for a comprehensive review of tropomyosin biology. I realised that the field was simply beyond the capacity of any one person to do the field j- tice.

Actin-Binding Proteins and Disease

Actin-Binding Proteins and Disease
Author: Cris dos Remedios
Publisher: Springer Science & Business Media
Total Pages: 362
Release: 2008-01-08
Genre: Science
ISBN: 0387717498

There are scattered reports in the published literature citing relationships between actin, actin-binding proteins and disease. This volume brings this information together for the first time, with a focus on human disorders. The volume is relevant to a wide readership including cell biologists interested in understanding how structural and functional changes in proteins impact on the organism as a whole.

Molecular Mechanisms of Isoform-dependent Interactions of Proteins from the Tropomodulin Family with Their Binding Partners

Molecular Mechanisms of Isoform-dependent Interactions of Proteins from the Tropomodulin Family with Their Binding Partners
Author: Mert Colpan
Publisher:
Total Pages: 201
Release: 2016
Genre:
ISBN:

Actin filaments are major components of the cytoskeleton in eukaryotic cells and are involved in vital cellular functions such as cell motility and muscle contraction. Polymerization of actin filament is regulated by fast-growing (barbed) end and slow-growing (pointed) end-binding proteins. Proteins of the tropomodulin (Tmod) family bind to the pointed end of actin filaments in a tropomyosin (TM)-dependent fashion. Tmod isoforms cap the pointed end to inhibit actin polymerization or depolymerization, whereas leiomodin (Lmod) isoforms allow actin filaments to elongate from this end.

Actin-Monomer-Binding Proteins

Actin-Monomer-Binding Proteins
Author: Pekka Lappalainen
Publisher: Springer Science & Business Media
Total Pages: 118
Release: 2008-05-14
Genre: Science
ISBN: 0387464077

This book provides a comprehensive view on actin monomer-binding proteins and the mechanisms by which they contribute to actin dynamics and various actin-dependent cellular processes. This new title contains chapters that describe the basic mechanisms of actin dynamics as well as the structural principles by which various actin-binding proteins interact with actin. The book is suitable further reading for students in advanced cell biology classes.

Deciphering the Tropomyosin Code: Uncovering How Different Tropomyosin Isoforms Bind and Assemble on Actin Filaments

Deciphering the Tropomyosin Code: Uncovering How Different Tropomyosin Isoforms Bind and Assemble on Actin Filaments
Author: Johnny Rodriguez
Publisher:
Total Pages:
Release: 2020
Genre:
ISBN:

Actin is a highly conserved protein that assembles into many three-dimensional structures, each with a unique subset of actin-binding proteins that produces a unique three-dimensional architecture capable of performing a specific function. These actin networks are central to cellular processes such as motility, adhesion, endocytosis, and division. Yet how actin filaments can recruit the correct subset of actin-binding proteins while avoiding the incorrect ones remains unclear. Recent literature demonstrated that in non-muscle cells, a different tropomyosin isoform(s) is present at every single actin network. Tropomyosins are coiled-coil proteins that regulate access to actin filament binding sites and now widely believed to determine which actin structure will be built. Despite this, we know very little about the assembly and function of tropomyosins on actin filaments. This is partly due to the fact that mammalian cells express over 20 different tropomyosin isoforms. In the Mullins lab, we have chosen Drosophila melanogaster S2 cells as the model system for the study of tropomyosins because S2 cells are easy to grow, highly susceptible to gene inhibition using RNAi, have well-characterized actin networks, and most importantly, only express three tropomyosin isoforms. In this thesis, we investigate how these Drosophila tropomyosins assemble on actin filaments. In Chapter 1, we designed a microfluidic system that allows us to manipulate microscopy experiments at a level never before achieved in the Mullins lab. In Chapter 2, we characterize binding and dynamic properties of the classic Drosophila tropomyosin Tm1A. In Chapter 3, we discovered how to get Drosophila tropomyosins Tm1J and Tm2A to bind actin filaments and then characterize these tropomyosins.

Molecular Interactions of Actin

Molecular Interactions of Actin
Author: C.G. dos Remedios
Publisher: Springer Science & Business Media
Total Pages: 272
Release: 2012-12-06
Genre: Science
ISBN: 354046560X

Actin is one of the most widespread proteins in eukaryotic cells. This book and its companion (Molecular Interactions of Actin. Actin-Myosin Interaction, Actin-Based Regulation) provide an authoritative and opinionated view of the structure and function of this essential protein. Each section includes an historical perspective and a detailed commentary on actin protein chemistry, molecular and cell biology of actin. While some chapters review the body of knowledge of the subject, others contain new experimental data. This book will appeal to research scientists seeking contemporary overviews of actin and its binding proteins. Contributors include senior scientists as well as the new breed of younger scientists.

Scientific Report

Scientific Report
Author: Scripps Research Institute
Publisher:
Total Pages: 392
Release: 2001
Genre: Biochemistry
ISBN:

Fibrous Proteins: Structures and Mechanisms

Fibrous Proteins: Structures and Mechanisms
Author: David A.D. Parry
Publisher: Springer
Total Pages: 630
Release: 2017-01-18
Genre: Science
ISBN: 3319496743

This book provides the readers with an up-to-date review of the design, structure and function of a representative selection of fibrous proteins in both health and disease. The importance of the α-helical coiled coil, a conformational motif based on the heptad repeat in the amino acid sequence of all α-fibrous proteins (and parts of some globular proteins) is underlined by three Chapters devoted to its design, structure, function and topology. Specific proteins covered in the text and which depend on the coiled coil for their structure and function, include the intermediate filament proteins, tropomyosin, myosin, paramyosin, fibrin and members of the spectrin superfamily. Also described are fibrous proteins based on the β-pleated sheet and collagen conformations. Recombinant structural proteins, especially of silk and collagen, are discussed in the context of developing new biomaterials with varied applications. Established researchers and postgraduate students in the fields of protein chemistry, biochemistry and structural biophysics will find Fibrous Proteins: Structures and Mechanisms to be an invaluable collection of topical reviews that describe the basic advances made in the field of fibrous proteins over the past decade. This book, written by recognized authorities in the field, provides a clear account of the current status of fibrous protein research and, in addition, establishes the basis for deciding the most appropriate directions for future activity, including the applications of protein engineering and the commercial exploitation of new biomaterials.