Dia1

Glioblastomas (GBM) are aggressive tumors that lack effective treatments. Here, we show that the Rho family guanine nucleotide exchange factor Syx promotes GBM cell growth both in vitro and in orthotopic xenografts derived from patients with GBM. Growth defects upon Syx depletion are attributed to prolonged mitosis, increased DNA damage, G2/M cell cycle arrest, and cell apoptosis, mediated by altered mRNA and protein expression of various cell cycle regulators. These effects are phenocopied by depletion of the Rho downstream effector Dia1 and are due, at least in part, to increased phosphorylation, cytoplasmic retention, and reduced activity of the YAP/TAZ transcriptional coactivators...

Although implicated in adhesion, only a few studies address how the actin assembly factors guide cell positioning in multicellular tissues. The formin, Dia1, localizes to the proliferative basal layer of the epidermis. In organotypic cultures, Dia1 depletion reduced basal cell density and resulted in stratified tissues with disorganized differentiation and proliferative markers. Since crowding induces differentiation in epidermal tissues, we hypothesized that Dia1 is essential to reach densities amenable to differentiation before or during stratification...

BACKGROUND: Methemoglobin is the reduced form of haemoglobin that is normally found in the blood in levels < 1%. Methemoglobinemia can occur as a congenital or acquired disease. Two types of recessive congenital methaemoglobinemia (RCM) are caused by the NADH-dependent cytochrome b5 reductase enzyme deficiency of the CYB5R3 gene. RCM-I is characterized by higher methaemoglobin levels (> 2 g/dL), causing only cyanosis, whereas RCM-II is associated with cyanosis with neurological impairment...

Plasticity of cell mechanics underlies a wide range of cell and tissue behaviors allowing cells to migrate through narrow spaces, resist shear forces, and safeguard against mechanical damage. Such plasticity depends on spatiotemporal regulation of the actomyosin cytoskeleton, but mechanisms of adaptive change in cell mechanics remain elusive. Here, we report a mechanism of mechanically activated actin polymerization at focal adhesions (FAs), specifically requiring the actin elongation factor mDia1. By combining live-cell imaging with mathematical modeling, we show that actin polymerization at FAs exhibits pulsatile dynamics where spikes of mDia1 activity are triggered by contractile forces...

T-cell receptor stimulation induces the convergence of multivesicular bodies towards the microtubule-organizing centre (MTOC) and the polarization of the MTOC to the immune synapse (IS). These events lead to exosome secretion at the IS. We describe here that upon IS formation centrosomal area F-actin decreased concomitantly with MTOC polarization to the IS. PKCδ-interfered T cell clones showed a sustained level of centrosomal area F-actin associated with defective MTOC polarization. We analysed the contribution of two actin cytoskeleton-regulatory proteins, FMNL1 and paxillin, to the regulation of cortical and centrosomal F-actin networks...

Dia1, which belongs to the diaphanous-related formin family, influences a variety of cellular processes through straight actin elongation activity. Recently, novel DIA1 mutants such as p.R1213X (p.R1204X) and p.A265S, have been reported to cause an autosomal dominant sensorineural hearing loss (DFNA1). Additionally, active DIA1 mutants induce progressive hearing loss in a gain-of-function manner. However, the subcellular localization and pathological function of DIA1(R1213X/R1204X) remains unknown. In the present study, we demonstrated the localization of endogenous Dia1 and the constitutively active DIA1 mutant in the cochlea, using transgenic mice expressing FLAG-tagged DIA1(R1204X) (DIA1-TG)...

Formins and tropomyosins (Tpms) are two central components of the microfilaments. Formins are involved in the nucleation and polymerization of actin filaments, and Tpms form along the actin stress fibers to regulate their dynamics. However, the correlation between formins and Tpms remains unclear. Here, we elucidated the function of distinct formins and their specific regulation to the subcellular-localization of Tpm isoforms on dorsal stress fibers in human osteosarcoma cells. Knockdown of individual formin isoform led to varied defects in actin stress fiber network, but did not affect the expression level of other formin isoforms and Tpms...

BACKGROUND: Diaphanous-related formin 1 (DIA1), which assembles the unbranched actin microfilament and microtubule cytoskeleton, is encoded by DIAPH1 . Constitutive activation by the disruption of autoinhibitory interactions between the N-terminal diaphanous inhibitory domain (DID) and C-terminal diaphanous autoregulatory domain (DAD) dysregulates DIA1, resulting in both hearing loss and blood cell abnormalities. METHODS AND RESULTS: Here, we report the first constitutively active mutant in the DID (p...

The primary cilium is a single non-motile protrusion of the plasma membrane of most types of mammalian cell. The structure, length and function of the primary cilium must be tightly controlled because their dysfunction is associated with disease. Caveolin 1 (Cav1), which is best known as a component of membrane invaginations called caveolae, is also present in non-caveolar membrane domains whose function is beginning to be understood. We show that silencing of α and β Cav1 isoforms in different cell lines increases ciliary length regardless of the route of primary ciliogenesis...

Many kinases are still 'orphans,' which means knowledge about their substrates, and often also about the processes they regulate, is lacking. Here, DIA1/C3orf58, a member of a novel predicted kinase-like family, is shown to be present in the endoplasmic reticulum and to influence trafficking via the secretory pathway. Subsequently, DIA1 is subjected to phosphoproteomics analysis to cast light on its signalling pathways. A liquid chromatography-tandem mass spectrometry proteomic approach with phosphopeptide enrichment is applied to membrane fractions of DIA1-overexpressing and control HEK293T cells, and phosphosites dependent on the presence of DIA1 are elucidated...

Developing tissues change shape and tumors initiate spreading through collective cell motility. Conserved mechanisms by which tissues initiate motility into their surroundings are not known. We investigated cytoskeletal regulators during collective invasion by mouse tumor organoids and epithelial Madin-Darby canine kidney (MDCK) acini undergoing branching morphogenesis in collagen. Use of the broad-spectrum formin inhibitor SMIFH2 prevented the formation of migrating cell fronts in both cell types. Focusing on the role of the formin Dia1 in branching morphogenesis, we found that its depletion in MDCK cells does not alter planar cell motility either within the acinus or in two-dimensional scattering assays...

Diaphanous (Dia)-related formins (DRFs) coordinate cytoskeletal remodeling by controlling actin nucleation and microtubule (MT) stabilization to facilitate processes such as cell polarization and migration; yet the full extent of their activities remains unknown. Here, we uncover two discrete roles and functions of DRFs during early human immunodeficiency virus type 1 (HIV-1) infection. Independent of their actin regulatory activities, Dia1 and Dia2 facilitated HIV-1-induced MT stabilization and the intracellular motility of virus particles...

Hair cells in the cochlea display highly regulated actin polymerization, which is mediated by the human diaphanous-related formin 1 gene (DIAPH1; also called DFNA1, DIA1). DFNA1, the first type of autosomal dominant nonsyndromic hearing loss (ADNSHL), is known to be associated with mutations in DIAPH1. However, no genetic study of DFNA1 in Koreans with hearing loss has yet been reported. A 51-year-old patient in a Korean family with ADNSHL was examined by pure-tone audiometry, and genetic analysis of DIAPH1 was performed...

DIAPH1 encodes human DIA1, a formin protein that elongates unbranched actin. The c.3634+1G>T DIAPH1 mutation causes autosomal dominant nonsyndromic sensorineural hearing loss, DFNA1, characterized by progressive deafness starting in childhood. The mutation occurs near the C-terminus of the diaphanous autoregulatory domain (DAD) of DIA1, which interacts with its N-terminal diaphanous inhibitory domain (DID), and may engender constitutive activation of DIA1. However, the underlying pathogenesis that causes DFNA1 is unclear...

INTRODUCTION: RhoA has been shown to be beneficial in cardiac disease models when overexpressed in cardiomyocytes, whereas its role in cardiac fibroblasts (CF) is still poorly understood. During cardiac remodeling CF undergo a transition towards a myofibroblast phenotype thereby showing an increased proliferation and migration rate. Both processes involve the remodeling of the cytoskeleton. Since RhoA is known to be a major regulator of the cytoskeleton, we analyzed its role in CF and its effect on myofibroblast characteristics in 2 D and 3D models...

PURPOSE: To investigate the influence of prior high intensity double poling (DP) on physiological and biomechanical responses during subsequent diagonal stride (DIA). METHODS: Eight well-trained male cross-country skiers (age 22 ± 3 yr; VO2max 69 ± 3 ml · kg(-1) · min(-1)) roller-skied on a treadmill sequentially for 3 min at 90% DIA VO2max (DIA1), 3 min at 90% DP VO2peak and 3 min at 90% DIA VO2max (DIA2). Cardio-respiratory responses were monitored continuously and gases and metabolites in blood from the a...

Homotypic or entotic cell-in-cell invasion is an integrin-independent process observed in carcinoma cells exposed during conditions of low adhesion such as in exudates of malignant disease. Although active cell-in-cell invasion depends on RhoA and actin, the precise mechanism as well as the underlying actin structures and assembly factors driving the process are unknown. Furthermore, whether specific cell surface receptors trigger entotic invasion in a signal-dependent fashion has not been investigated. In this study, we identify the G-protein-coupled LPA receptor 2 (LPAR2) as a signal transducer specifically required for the actively invading cell during entosis...

Rho GTPases are cytoskeleton-regulating proteins that mediate the formation of intercellular junctions. Their localized activation by Rho GEFs (guanine-nucleotide exchange factors) and the selective activation of downstream effectors have emerged as areas of active research in the cell adhesion field. We reported recently that the Rho-specific GEFs Syx (Synectin-binding RhoA exchange factor) and TEM4 (Tumor Endothelial Marker 4) are both essential for endothelial junction maturation and barrier function. Syx is recruited to cell contacts via its C-terminal PDZ binding motif and it's interaction with Mupp1 and the Crumbs polarity complex, while the junctional localization of TEM4 requires it's N-terminal domain and interaction with the cadherin-catenin complex...

Chloroplastic (NADP(+)) glyceraldehyde-3-phosphate dehydrogenase (E.C. 1.2.1.9) catalyzes the second reaction in photosynthesis after the fixation of carbon by RuBisCO. Chloroplast-bound (NADP(+)) G3PDH was resolved in soybean by starch gel electrophoresis using L-histidine-citrate buffer (pH 5.7). Histochemical staining revealed zymogram patterns indicative of a tetramer. A survey of soybean genotypes revealed differences in zymogram patterns between the principal cytoplasmic sources of the northern and southern US germplasms...

The role of RhoA in promoting directed cell migration has been complicated by studies showing that it is activated both in the front and the rear of migrating cells. We report here that the RhoA-specific guanine nucleotide exchange factor Syx is required for the polarity of actively migrating brain and breast tumor cells. This function of Syx is mediated by the selective activation of the RhoA downstream effector Dia1, the subsequent reorganization of microtubules, and the downregulation of focal adhesions and actin stress fibers...