In many eukaryotic lineages, the RHO clade of small GTPases controls microfilament dynamics by direct binding to formin family actin nucleators. A new study in plants reveals that formin activity can also be regulated by a RHO cofactor rather than the GTPase itself.

• MeSH
• Actins metabolism   MeSH
• Formins * metabolism   genetics   MeSH
• Actin Cytoskeleton metabolism   MeSH
• Microfilament Proteins metabolism   genetics   MeSH
• rho GTP-Binding Proteins metabolism   genetics   MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Actins MeSH
• Formins * MeSH
• Microfilament Proteins MeSH
• rho GTP-Binding Proteins MeSH

Formins are a large, evolutionarily old family of cytoskeletal regulators whose roles include actin capping and nucleation, as well as modulation of microtubule dynamics. The plant class I formin clade is characterized by a unique domain organization, as most of its members are transmembrane proteins with possible cell wall-binding motifs exposed to the extracytoplasmic space-a structure that appears to be a synapomorphy of the plant kingdom. While such transmembrane formins are traditionally considered mainly as plasmalemma-localized proteins contributing to the organization of the cell cortex, we review, from a cell biology perspective, the growing evidence that they can also, at least temporarily, reside (and in some cases also function) in endomembranes including secretory and endocytotic pathway compartments, the endoplasmic reticulum, the nuclear envelope, and the tonoplast. Based on this evidence, we propose that class I formins may thus serve as 'active cargoes' of membrane trafficking-membrane-embedded proteins that modulate the fate of endo- or exocytotic compartments while being transported by them.

• Keywords
• Actin, biotic interactions, cell growth, cytokinesis, endocytosis, exocytosis, formin, microtubules, plasmalemma, tonoplast,
• MeSH
• Cell Membrane * metabolism   MeSH
• Formins * metabolism   MeSH
• Membrane Proteins metabolism   genetics   MeSH
• Plant Proteins metabolism   genetics   MeSH
• Protein Transport * MeSH
• Publication type
• Journal Article MeSH
• Review MeSH
• Names of Substances
• Formins * MeSH
• Membrane Proteins MeSH
• Plant Proteins MeSH

Proteins participating in plant cell morphogenesis are often encoded by large gene families, in some cases comprising paralogs with variable (modular) domain organization, as in the case of the formin (FH2 protein) family of actin nucleators that can have also additional functions. Unravelling the phylogeny of such a complex gene family brings a number of specific challenges but may be crucial for predictions of protein function and for experimental design. Here we present an overview of our "cottage industry" semi-manual bioinformatic approach, based mostly, though not exclusively, on freely available software tools, which we used to obtain insight into the evolutionary history of plant FH2 proteins and some other components of the plant cell morphogenesis apparatus.

• Keywords
• Formins, Molecular phylogenetics, Multidomain proteins, Multiple sequence alignment, Phylogenetic tree construction, Splicing prediction, Transcriptome analysis,
• MeSH
• Actins * metabolism   MeSH
• Formins metabolism   MeSH
• Plant Proteins * metabolism   MeSH
• Protein Structure, Tertiary MeSH
• Computational Biology MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Review MeSH
• Names of Substances
• Actins * MeSH
• Formins MeSH
• Plant Proteins * MeSH

The phragmoplast separates daughter cells during cytokinesis by constructing the cell plate, which depends on interaction between cytoskeleton and membrane compartments. Proteins responsible for these interactions remain unknown, but formins can link cytoskeleton with membranes and several members of formin protein family localize to the cell plate. Progress in functional characterization of formins in cytokinesis is hindered by functional redundancies within the large formin gene family. We addressed this limitation by employing Small Molecular Inhibitor of Formin Homology 2 (SMIFH2), a small-molecule inhibitor of formins. Treatment of tobacco (Nicotiana tabacum) tissue culture cells with SMIFH2 perturbed localization of actin at the cell plate; slowed down both microtubule polymerization and phragmoplast expansion; diminished association of dynamin-related proteins with the cell plate independently of actin and microtubules; and caused cell plate swelling. Another impact of SMIFH2 was shortening of the END BINDING1b (EB1b) and EB1c comets on the growing microtubule plus ends in N. tabacum tissue culture cells and Arabidopsis thaliana cotyledon epidermis cells. The shape of the EB1 comets in the SMIFH2-treated cells resembled that of the knockdown mutant of plant Xenopus Microtubule-Associated protein of 215 kDa (XMAP215) homolog MICROTUBULE ORGANIZATION 1/GEMINI 1 (MOR1/GEM1). This outcome suggests that formins promote elongation of tubulin flares on the growing plus ends. Formins AtFH1 (A. thaliana Formin Homology 1) and AtFH8 can also interact with EB1. Besides cytokinesis, formins function in the mitotic spindle assembly and metaphase to anaphase transition. Our data suggest that during cytokinesis formins function in: (1) promoting microtubule polymerization; (2) nucleating F-actin at the cell plate; (3) retaining dynamin-related proteins at the cell plate; and (4) remodeling of the cell plate membrane.

• MeSH
• Actins metabolism   MeSH
• Arabidopsis drug effects   genetics   physiology   MeSH
• Cytokinesis drug effects   genetics   MeSH
• Cytoskeleton drug effects   metabolism   MeSH
• Formins genetics   metabolism   MeSH
• Microtubules drug effects   metabolism   MeSH
• Nicotiana drug effects   genetics   physiology   MeSH
• Thiones pharmacology   MeSH
• Tubulin metabolism   MeSH
• Uracil analogs & derivatives   pharmacology   MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Research Support, U.S. Gov't, Non-P.H.S. MeSH
• Names of Substances
• Actins MeSH
• Formins MeSH
• SMIFH2 compound MeSH Browser
• Thiones MeSH
• Tubulin MeSH
• Uracil MeSH

Profilin 1 is a crucial actin regulator, interacting with monomeric actin and several actin-binding proteins controlling actin polymerization. Recently, it has become evident that this profilin isoform associates with microtubules via formins and interferes with microtubule elongation at the cell periphery. Recruitment of microtubule-associated profilin upon extensive actin polymerizations, for example, at the cell edge, enhances microtubule growth, indicating that profilin contributes to the coordination of actin and microtubule organization. Here, we provide further evidence for the profilin-microtubule connection by demonstrating that it also functions in centrosomes where it impacts on microtubule nucleation.

• MeSH
• Actins metabolism   MeSH
• Caco-2 Cells MeSH
• Centrosome metabolism   MeSH
• Formins metabolism   MeSH
• Gene Knockout Techniques MeSH
• Humans MeSH
• Melanoma, Experimental metabolism   pathology   MeSH
• Microfilament Proteins metabolism   MeSH
• Microtubules metabolism   MeSH
• Mice MeSH
• Skin Neoplasms metabolism   pathology   MeSH
• Polymerization MeSH
• Profilins genetics   metabolism   MeSH
• Signal Transduction genetics   MeSH
• Transfection MeSH
• Tubulin metabolism   MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Actins MeSH
• Formins MeSH
• Microfilament Proteins MeSH
• PFN1 protein, human MeSH Browser
• Pfn1 protein, mouse MeSH Browser
• Profilins MeSH
• Tubulin MeSH

Formins are evolutionarily conserved multi-domain proteins participating in the control of both actin and microtubule dynamics. Angiosperm formins form two evolutionarily distinct families, Class I and Class II, with class-specific domain layouts. The model plant Arabidopsis thaliana has 21 formin-encoding loci, including 10 Class II members. In this study, we analyze the subcellular localization of two A. thaliana Class II formins exhibiting typical domain organization, the so far uncharacterized formin AtFH13 (At5g58160) and its distant homolog AtFH14 (At1g31810), previously reported to bind microtubules. Fluorescent protein-tagged full length formins and their individual domains were transiently expressed in Nicotiana benthamiana leaves under the control of a constitutive promoter and their subcellular localization (including co-localization with cytoskeletal structures and the endoplasmic reticulum) was examined using confocal microscopy. While the two formins exhibit distinct and only partially overlapping localization patterns, they both associate with microtubules via the conserved formin homology 2 (FH2) domain and with the periphery of the endoplasmic reticulum, at least in part via the N-terminal PTEN (Phosphatase and Tensin)-like domain. Surprisingly, FH2 domains of AtFH13 and AtFH14 can form heterodimers in the yeast two-hybrid assay-a first case of potentially biologically relevant formin heterodimerization mediated solely by the FH2 domain.

• Keywords
• At1g31810, At5g58160, AtFH13, AtFH14, FH2 domain, PTEN-like domain, class II formin, confocal laser scanning microscopy,
• MeSH
• Arabidopsis genetics   metabolism   MeSH
• Dimerization MeSH
• Endoplasmic Reticulum metabolism   MeSH
• Gene Expression MeSH
• Formins genetics   metabolism   MeSH
• Microtubules metabolism   MeSH
• Protein Domains MeSH
• Arabidopsis Proteins genetics   metabolism   MeSH
• Recombinant Proteins genetics   metabolism   MeSH
• Nicotiana metabolism   MeSH
• Protein Binding MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Formins MeSH
• Arabidopsis Proteins MeSH
• Recombinant Proteins MeSH

BACKGROUND: Mutations in INF2 are frequently responsible for focal segmental glomerulosclerosis (FSGS), which is a common cause of end stage renal disease (ESRD); additionally, they are also connected with Charcot-Marie-Tooth neuropathy. INF2 encodes for inverted formin 2. This protein participates in regulation of the dynamics of the actin cytoskeleton, involving not only the polymerisation, but also the depolymerisation of filaments. The present study is the first mutational analysis of INF2 done in the Czech Republic. METHODS: Mutational analysis of INF2 was performed on 109 patients (mean age at onset 41.44 ± 18.91 years) with FSGS or minimal change disease (MCD); and also in 6 patients without renal biopsy who had already developed chronic kidney disease (CKD)/ESRD at the time of diagnosis. We used high resolution melting method (HRM), with subsequent Sanger sequencing, in suspect samples from HRM analysis. The HRM method is an effective method for the screening of large cohorts of patients. RESULTS: Two pathogenic mutations (p.Arg214His and p.Arg218Gln) were detected in INF2. The first (p.Arg214His) was identified in the FSGS patient with a positive family history. The second mutation (p.Arg218Gln) was found in two brothers with ESRD of unknown etiology. The most frequent sequence change was the substitution p.P35P, the incidence of which corresponded with the frequencies available in the ExAC Browser and gnomAD Browser databases. This analysis also detected different exonic and intronic changes that probably did not influence the phenotype of the included patients. CONCLUSIONS: The INF2 mutational screening is useful in familial FSGS cases as well as in patients with an unknown cause for their ESRD, but with a positive family history. INF2 seems to be not only the cause of FSGS, but also of ESRD of unknown etiology. Our study has confirmed that the HRM analysis is a very useful method for the identification of single nucleotide substitutions.

• Keywords
• End stage renal disease, Focal segmental glomerulosclerosis, High resolution melting method, INF2, Minimal change disease,
• MeSH
• Charcot-Marie-Tooth Disease genetics   metabolism   MeSH
• Kidney Failure, Chronic genetics   metabolism   MeSH
• Adult MeSH
• Exons genetics   MeSH
• Phenotype MeSH
• Glomerulosclerosis, Focal Segmental genetics   metabolism   MeSH
• Formins MeSH
• Introns genetics   MeSH
• Cohort Studies MeSH
• Humans MeSH
• Microfilament Proteins genetics   metabolism   MeSH
• Mutation genetics   MeSH
• DNA Mutational Analysis methods   MeSH
• Check Tag
• Adult MeSH
• Humans MeSH
• Male MeSH
• Female MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Geographicals
• Czech Republic MeSH
• Names of Substances
• Formins MeSH
• INF2 protein, human MeSH Browser
• Microfilament Proteins MeSH

Age-associated memory decline is due to variable combinations of genetic and environmental risk factors. How these risk factors interact to drive disease onset is currently unknown. Here we begin to elucidate the mechanisms by which post-traumatic stress disorder (PTSD) at a young age contributes to an increased risk to develop dementia at old age. We show that the actin nucleator Formin 2 (Fmn2) is deregulated in PTSD and in Alzheimer's disease (AD) patients. Young mice lacking the Fmn2 gene exhibit PTSD-like phenotypes and corresponding impairments of synaptic plasticity, while the consolidation of new memories is unaffected. However, Fmn2 mutant mice develop accelerated age-associated memory decline that is further increased in the presence of additional risk factors and is mechanistically linked to a loss of transcriptional homeostasis. In conclusion, our data present a new approach to explore the connection between AD risk factors across life span and provide mechanistic insight to the processes by which neuropsychiatric diseases at a young age affect the risk for developing dementia.

• Keywords
• Alzheimer's disease, Formin 2, HDAC inhibitor, aging, post‐traumatic stress disorder,
• MeSH
• Dementia epidemiology   genetics   psychology   MeSH
• Adult MeSH
• Phenotype MeSH
• Formins MeSH
• Nuclear Proteins genetics   MeSH
• Middle Aged MeSH
• Humans MeSH
• Microfilament Proteins genetics   MeSH
• Mice, Knockout MeSH
• Mice MeSH
• Neuronal Plasticity genetics   MeSH
• Memory physiology   MeSH
• Stress Disorders, Post-Traumatic complications   epidemiology   genetics   MeSH
• Nerve Tissue Proteins MeSH
• Risk Factors MeSH
• Aging genetics   physiology   MeSH
• Case-Control Studies MeSH
• Age of Onset MeSH
• Animals MeSH
• Check Tag
• Adult MeSH
• Middle Aged MeSH
• Humans MeSH
• Male MeSH
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• formin 2 protein, mouse MeSH Browser
• Formins MeSH
• Nuclear Proteins MeSH
• Microfilament Proteins MeSH
• Nerve Tissue Proteins MeSH

Actin-associated proteins regulate multiple cellular processes, including proliferation and differentiation, but the molecular mechanisms underlying these processes are unclear. Here, we report that the actin-binding protein filamin A (FlnA) physically interacts with the actin-nucleating protein formin 2 (Fmn2). Loss of FlnA and Fmn2 impairs proliferation, thereby generating multiple embryonic phenotypes, including microcephaly. FlnA interacts with the Wnt co-receptor Lrp6. Loss of FlnA and Fmn2 impairs Lrp6 endocytosis, downstream Gsk3β activity, and β-catenin accumulation in the nucleus. The proliferative defect in Flna and Fmn2 null neural progenitors is rescued by inhibiting Gsk3β activity. Our findings thus reveal a novel mechanism whereby actin-associated proteins regulate proliferation by mediating the endocytosis and transportation of components in the canonical Wnt pathway. Moreover, the Fmn2-dependent signaling in this pathway parallels that seen in the non-canonical Wnt-dependent regulation of planar cell polarity through the Formin homology protein Daam. These studies provide evidence for integration of actin-associated processes in directing neuroepithelial proliferation.

• Keywords
• Differentiation, Endocytosis, Filamin, Formin, Lrp6, Neural progenitor, Proliferation, Vesicle trafficking,
• MeSH
• beta Catenin metabolism   MeSH
• Cell Differentiation MeSH
• Cell Membrane physiology   MeSH
• Cell Line MeSH
• Endocytosis physiology   MeSH
• Filamins genetics   metabolism   MeSH
• Formins MeSH
• HEK293 Cells MeSH
• Nuclear Proteins genetics   metabolism   MeSH
• Glycogen Synthase Kinase 3 beta antagonists & inhibitors   metabolism   MeSH
• Low Density Lipoprotein Receptor-Related Protein-6 metabolism   MeSH
• Humans MeSH
• Microcephaly genetics   MeSH
• Microfilament Proteins genetics   metabolism   MeSH
• Mice, Knockout MeSH
• Mice MeSH
• Cell Proliferation genetics   physiology   MeSH
• Nerve Tissue Proteins MeSH
• Wnt Proteins metabolism   MeSH
• Wnt Signaling Pathway physiology   MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• beta Catenin MeSH
• Filamins MeSH
• FlnA protein, mouse MeSH Browser
• formin 2 protein, mouse MeSH Browser
• Formins MeSH
• Nuclear Proteins MeSH
• Glycogen Synthase Kinase 3 beta MeSH
• Low Density Lipoprotein Receptor-Related Protein-6 MeSH
• Lrp6 protein, mouse MeSH Browser
• Microfilament Proteins MeSH
• Nerve Tissue Proteins MeSH
• Wnt Proteins MeSH

Development of the plant aerial organs epidermis involves a complex interplay of cytoskeletal rearrangements, membrane trafficking-dependent cell surface expansion, and intra- and intercellular signaling, resulting in a pattern of perfectly interlocking pavement cells. While recent detailed in vivo observations convincingly identify microtubules rather than actin as key players at the early stages of development of pavement cell lobes in Arabidopsis, mutations affecting the actin-nucleating ARP2/3 complex are long known to reduce pavement cell lobing, suggesting a central role for actin. We have now shown that functional impairment of the Arabidopsis formin FH1 enhances both microtubule dynamics and pavement cell lobing. While formins are best known for their ability to nucleate actin, many members of this old gene family now emerge as direct or indirect regulators of the microtubule cytoskeleton, and our findings suggest that they might co-ordinate action of the two cytoskeletal systems during pavement cell morphogenesis.

• Keywords
• Actin, FH2 proteins, cell growth, epidermal pavement cells, formins, microtubules,
• MeSH
• Arabidopsis growth & development   metabolism   ultrastructure   MeSH
• Models, Biological MeSH
• Cytoskeleton metabolism   physiology   ultrastructure   MeSH
• Formins MeSH
• Membrane Proteins genetics   metabolism   physiology   MeSH
• Microtubules metabolism   physiology   ultrastructure   MeSH
• Multigene Family MeSH
• Arabidopsis Proteins genetics   metabolism   physiology   MeSH
• Plant Cells metabolism   ultrastructure   MeSH
• Signal Transduction MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• AFH1 protein, Arabidopsis MeSH Browser
• Formins MeSH
• Membrane Proteins MeSH
• Arabidopsis Proteins MeSH