-
European Journal of Cell Biology 2022For cells to adhere, migrate and proliferate, remodeling of the actin cytoskeleton is required. This process consumes a large amount of ATP while having an intimate...
For cells to adhere, migrate and proliferate, remodeling of the actin cytoskeleton is required. This process consumes a large amount of ATP while having an intimate connection with cellular metabolism. Signaling pathways that regulate energy homeostasis can also affect actin dynamics, whereas a variety of actin binding proteins directly or indirectly interact with the anabolic and catabolic regulators in cells. Here, we discuss the inter-regulation between actin filaments and cellular metabolism, reviewing recent discoveries on key metabolic enzymes that respond to actin remodeling as well as historical findings on metabolic stress-induced cytoskeletal reorganization. We also address emerging techniques that would benefit the study of cytoskeletal dynamics and cellular metabolism in high spatial-temporal resolution.
Topics: Actins; Actin Cytoskeleton; Cytoskeleton; Microfilament Proteins
PubMed: 36343493
DOI: 10.1016/j.ejcb.2022.151281 -
Cancer Science Oct 2017Cancer is a polygenic disease characterized by uncontrolled growth of normal body cells, deregulation of the cell cycle as well as resistance to apoptosis. The... (Review)
Review
Cancer is a polygenic disease characterized by uncontrolled growth of normal body cells, deregulation of the cell cycle as well as resistance to apoptosis. The spectraplakin protein microtubule actin cross-linking factor 1 (MACF1) plays an essential function in various cellular processes, including cell proliferation, migration, signaling transduction and embryo development. MACF1 is also involved in processes such as metastatic invasion in which cytoskeleton organization is a critical element that contributes to tumor progression in various human cancers. Aberrant expression of MACF1 initiates the tumor cell proliferation, and migration and metastasis in numerous cancers, such as breast cancer, colon cancer, lung cancer and glioblastoma. In this review, we summarized the current knowledge of MACF1 and its critical role in different human cancers. This will be helpful for researchers to investigate the novel functional role of MACF1 in human cancers and as a potential target to enhance the efficacy of therapeutic treatment modalities.
Topics: Alternative Splicing; Cell Movement; Cell Proliferation; Disease Progression; Humans; Microfilament Proteins; Neoplasm Invasiveness; Neoplasms; Signal Transduction
PubMed: 28782898
DOI: 10.1111/cas.13344 -
Journal of Cell Science Jul 2022In formin-family proteins, actin filament nucleation and elongation activities reside in the formin homology 1 (FH1) and FH2 domains, with reaction rates that vary by at...
In formin-family proteins, actin filament nucleation and elongation activities reside in the formin homology 1 (FH1) and FH2 domains, with reaction rates that vary by at least 20-fold between formins. Each cell expresses distinct formins that assemble one or several actin structures, raising the question of what confers each formin its specificity. Here, using the formin Fus1 in Schizosaccharomyces pombe, we systematically probed the importance of formin nucleation and elongation rates in vivo. Fus1 assembles the actin fusion focus, necessary for gamete fusion to form the zygote during sexual reproduction. By constructing chimeric formins with combinations of FH1 and FH2 domains previously characterized in vitro, we establish that changes in formin nucleation and elongation rates have direct consequences on fusion focus architecture, and that Fus1 native high nucleation and low elongation rates are optimal for fusion focus assembly. We further describe a point mutant in Fus1 FH2 that preserves native nucleation and elongation rates in vitro but alters function in vivo, indicating an additional FH2 domain property. Thus, rates of actin assembly are tailored for assembly of specific actin structures.
Topics: Actin Cytoskeleton; Actins; Formins; Microfilament Proteins; Schizosaccharomyces; Schizosaccharomyces pombe Proteins
PubMed: 35673994
DOI: 10.1242/jcs.260289 -
Biophysical Journal Jun 2022Actin is one of the key structural components of the eukaryotic cytoskeleton that regulates cellular architecture and mechanical properties. Dynamic regulation of actin...
Actin is one of the key structural components of the eukaryotic cytoskeleton that regulates cellular architecture and mechanical properties. Dynamic regulation of actin filament length and organization is essential for the control of many physiological processes including cell adhesion, motility and division. While previous studies have mostly focused on the mechanisms controlling the length of single actin filaments, it remains poorly understood how distinct actin filament populations in cells maintain different lengths using the same set of molecular building blocks. Here, we develop a theoretical model for the length regulation of multiple actin filaments by nucleation and growth-rate modulation by actin-binding proteins in a limiting pool of monomers. We first show that spontaneous nucleation of actin filaments naturally leads to heterogeneities in filament length distribution. We then investigate the effects of filament growth inhibition by capping proteins and growth promotion by formin proteins on filament length distribution. We find that filament length heterogeneity can be increased by growth inhibition, whereas growth promoters do not significantly affect length heterogeneity. Interestingly, a competition between filament growth inhibitors and growth promoters can give rise to bimodal filament length distribution as well as a highly heterogeneous length distribution with large statistical dispersion. We quantitatively predict how heterogeneity in actin filament length can be modulated by tuning filamentous actin nucleation and growth rates in order to create distinct filament subpopulations with different lengths.
Topics: Actin Cytoskeleton; Actins; Cytoskeleton; Eukaryotic Cells; Microfilament Proteins
PubMed: 35598045
DOI: 10.1016/j.bpj.2022.05.014 -
The Biochemical Journal Jan 2015The nematode Caenorhabditis elegans has two ADF (actin-depolymerizing factor)/cofilin isoforms, UNC-60A and UNC-60B, which are expressed by the unc60 gene by alternative...
The nematode Caenorhabditis elegans has two ADF (actin-depolymerizing factor)/cofilin isoforms, UNC-60A and UNC-60B, which are expressed by the unc60 gene by alternative splicing. UNC-60A has higher activity to cause net depolymerization, and to inhibit polymerization, than UNC-60B. UNC-60B, on the other hand, shows much stronger severing activity than UNC-60A. To understand the structural basis of their functional differences, we have determined the solution structures of UNC-60A and UNC-60B proteins and characterized their backbone dynamics. Both UNC-60A and UNC-60B show a conserved ADF/cofilin fold. The G-actin (globular actin)-binding regions of the two proteins are structurally and dynamically conserved. Accordingly, UNC-60A and UNC-60B individually bind to rabbit muscle ADP-G-actin with high affinities, with Kd values of 32.25 nM and 8.62 nM respectively. The primary differences between these strong and weak severing proteins were observed in the orientation and dynamics of the F-actin (filamentous actin)-binding loop (F-loop). In the strong severing activity isoform UNC-60B, the orientation of the F-loop was towards the recently identified F-loop-binding region on F-actin, and the F-loop was relatively more flexible with 14 residues showing motions on a nanosecond-picosecond timescale. In contrast, in the weak severing protein isoform UNC-60A, the orientation of the F-loop was away from the F-loop-binding region and inclined towards its own C-terminal and strand β6. It was also relatively less flexible with only five residues showing motions on a nanosecond-picosecond timescale. These differences in structure and dynamics seem to directly correlate with the differential F-actin site-binding and severing properties of UNC-60A and UNC-60B, and other related ADF/cofilin proteins.
Topics: Actin Depolymerizing Factors; Actins; Amino Acids; Animals; Caenorhabditis elegans; Caenorhabditis elegans Proteins; Destrin; Magnetic Resonance Spectroscopy; Microfilament Proteins; Nitrogen Isotopes; Protein Binding; Protein Structure, Secondary; Rabbits; Sequence Homology, Amino Acid; Solutions
PubMed: 25279657
DOI: 10.1042/BJ20140923 -
Journal of Cell Science Jan 2019Cellular contractility is governed by a control system of proteins that integrates internal and external cues to drive diverse shape change processes. This contractility...
Cellular contractility is governed by a control system of proteins that integrates internal and external cues to drive diverse shape change processes. This contractility controller includes myosin II motors, actin crosslinkers and protein scaffolds, which exhibit robust and cooperative mechanoaccumulation. However, the biochemical interactions and feedback mechanisms that drive the controller remain unknown. Here, we use a proteomics approach to identify direct interactors of two key nodes of the contractility controller in the social amoeba : the actin crosslinker cortexillin I and the scaffolding protein IQGAP2. We highlight several unexpected proteins that suggest feedback from metabolic and RNA-binding proteins on the contractility controller. Quantitative biochemical measurements reveal direct interactions between myosin II and cortexillin I, which form the core mechanosensor. Furthermore, IQGAP1 negatively regulates mechanoresponsiveness by competing with IQGAP2 for binding the myosin II-cortexillin I complex. These myosin II-cortexillin I-IQGAP2 complexes are pre-assembled into higher-order mechanoresponsive contractility kits (MCKs) that are poised to integrate into the cortex upon diffusional encounter coincident with mechanical inputs.This article has an associated First Person interview with the first author of the paper.
Topics: Actins; Cytoskeleton; Dictyostelium; Microfilament Proteins; Myosin Type II; Protozoan Proteins
PubMed: 30559246
DOI: 10.1242/jcs.226704 -
Developmental Dynamics : An Official... Nov 2021Lens morphogenesis, architecture, and clarity are known to be critically dependent on actin cytoskeleton organization and cell adhesive interactions. There is limited...
BACKGROUND
Lens morphogenesis, architecture, and clarity are known to be critically dependent on actin cytoskeleton organization and cell adhesive interactions. There is limited knowledge, however regarding the identity and role of key proteins regulating actin cytoskeletal organization in the lens. This study investigated the role of drebrin, a developmentally regulated actin-binding protein, in mouse lens development by generating and characterizing a conditional knockout (cKO) mouse model using the Cre-LoxP recombination approach.
RESULTS
Drebrin E, a splice variant of DBN1 is a predominant isoform expressed in the mouse lens and exhibits a maturation-dependent downregulation. Drebrin co-distributes with actin in both epithelium and fibers. Conditional deficiency (both haploinsufficiency and complete absence) of drebrin results in disrupted lens morphogenesis leading to cataract and microphthalmia. The drebrin cKO lens reveals a dramatic decrease in epithelial height and width, E-cadherin, and proliferation, and increased apoptotic cell death and expression of α-smooth muscle actin, together with severely impaired fiber cell organization, polarity, and cell-cell adhesion.
CONCLUSIONS
This study demonstrates the requirement of drebrin in lens development and growth, with drebrin deficiency leading to impaired lens morphogenesis and microphthalmia.
Topics: Actins; Animals; Cell Communication; Lens, Crystalline; Mice; Microfilament Proteins; Morphogenesis
PubMed: 33896079
DOI: 10.1002/dvdy.353 -
Physiological Reports Sep 2022Proteinuria is a major manifestation of kidney disease, reflecting injuries of glomerular podocytes. Actin cytoskeleton plays a pivotal role in stabilizing the foot...
Proteinuria is a major manifestation of kidney disease, reflecting injuries of glomerular podocytes. Actin cytoskeleton plays a pivotal role in stabilizing the foot processes of podocytes against the hydrostatic pressure of filtration. Calponin is an actin associated protein that regulates mechanical tension-related cytoskeleton functions and its role in podocytes has not been established. Here we studied the kidney phenotypes of calponin isoform 2 knockout (KO) mice. Urine samples were examined to quantify the ratio of albumin and creatinine. Kidney tissue samples were collected for histology and ultrastructural studies. A mouse podocyte cell line (E11) was used to study the expression and cellular localization of calponin 2. In comparison with wild-type (WT) controls, calponin 2 KO mice showed age-progressive high proteinuria and degeneration of renal glomeruli. High levels of calponin 2 are expressed in E11 podocytes and colocalized with actin stress fibers, tropomyosin and myosin IIA. Electron microscopy showed that aging calponin 2 KO mice had effacement of the podocyte foot processes and increased thickness of the glomerular basement membrane as compared to that of WT control. The findings demonstrate that deletion of calponin 2 aggravates age-progressive degeneration of the glomerular structure and function as filtration barrier. The critical role of calponin 2 in podocytes suggests a molecular target for understanding the pathogenesis of proteinuria and therapeutic development.
Topics: Actins; Albumins; Animals; Calcium-Binding Proteins; Calmodulin-Binding Proteins; Creatinine; Mice; Mice, Knockout; Microfilament Proteins; Nonmuscle Myosin Type IIA; Proteinuria; Tropomyosin; Calponins
PubMed: 36117313
DOI: 10.14814/phy2.15370 -
Kidney360 Jan 2022Ischemia-induced AKI resulting in tubular damage can often progress to CKD and is a common cause of nephrology consultation. After renal tubular epithelial damage,...
BACKGROUND
Ischemia-induced AKI resulting in tubular damage can often progress to CKD and is a common cause of nephrology consultation. After renal tubular epithelial damage, molecular and cellular mechanisms are activated to repair and regenerate the damaged epithelium. If these mechanisms are impaired, AKI can progress to CKD. Even in patients whose kidney function returns to normal baseline are more likely to develop CKD. Genome-wide association studies have provided robust evidence that genetic variants in Shroom3, which encodes an actin-associated protein, are associated with CKD and poor outcomes in transplanted kidneys. Here, we sought to further understand the associations of Shroom3 in CKD.
METHODS
Kidney ischemia was induced in wild-type (WT) and heterozygous null mice ( ) and the mechanisms of cellular recovery and repair were examined.
RESULTS
A 28-minute bilateral ischemia in mice resulted in 100% mortality within 24 hours. After 22-minute ischemic injury, mice had a 16% increased mortality, worsened kidney function, and significantly worse histopathology, apoptosis, proliferation, inflammation, and fibrosis after injury. The cortical tubular damage in was associated with disrupted epithelial redifferentiation, disrupted Rho-kinase/myosin signaling, and disorganized apical F-actin. Analysis of MDCK cells showed the levels of Shroom3 are directly correlated to apical organization of actin and actomyosin regulators.
CONCLUSION
These findings establish that Shroom3 is required for epithelial repair and redifferentiation through the organization of actomyosin regulators, and could explain why genetic variants in Shroom3 are associated with CKD and allograft rejection.
Topics: Acute Kidney Injury; Animals; Fibrosis; Genome-Wide Association Study; Humans; Kidney; Mice; Microfilament Proteins; Renal Insufficiency, Chronic
PubMed: 35368578
DOI: 10.34067/KID.0003802021 -
Scientific Reports Dec 2016The WD40 proteins, often acting as scaffolds to form functional complexes in fundamental cellular processes, are one of the largest families encoded by the eukaryotic...
The WD40 proteins, often acting as scaffolds to form functional complexes in fundamental cellular processes, are one of the largest families encoded by the eukaryotic genomes. Systematic studies of this family on genome scale are highly required for understanding their detailed functions, but are currently lacking in the animal lineage. Here we present a comprehensive in silico study of the human WD40 family. We have identified 262 non-redundant WD40 proteins, and grouped them into 21 classes according to their domain architectures. Among them, 11 animal-specific domain architectures have been recognized. Sequence alignment indicates the complicated duplication and recombination events in the evolution of this family. Through further phylogenetic analysis, we have revealed that the WD40 family underwent more expansion than the overall average in the evolutionary early stage, and the early emerged WD40 proteins are prone to domain architectures with fundamental cellular roles and more interactions. While most widely and highly expressed human WD40 genes originated early, the tissue-specific ones often have late origin. These results provide a landscape of the human WD40 family concerning their classification, evolution, and expression, serving as a valuable complement to the previous studies in the plant lineage.
Topics: Amino Acid Sequence; Animals; Cluster Analysis; Evolution, Molecular; Genome, Human; Humans; Microfilament Proteins; Multigene Family; Phylogeny; Plant Proteins; Plants; Sequence Alignment
PubMed: 27991561
DOI: 10.1038/srep39262