skip to main content


Title: LIM domain proteins in cell mechanobiology
Abstract

The actin cytoskeleton is important for maintaining mechanical homeostasis in adherent cells, largely through its regulation of adhesion and cortical tension. The LIM (Lin‐11,Isl1,MEC‐3) domain‐containing proteins are involved in a myriad of cellular mechanosensitive pathways. Recent work has discovered that LIM domains bind to mechanically stressed actin filaments, suggesting a novel and widely conserved mechanism of mechanosensing. This review summarizes the current state of knowledge of LIM protein mechanosensitivity.

 
more » « less
Award ID(s):
2011854
PAR ID:
10388092
Author(s) / Creator(s):
 ;  ;  ;  
Publisher / Repository:
Wiley Blackwell (John Wiley & Sons)
Date Published:
Journal Name:
Cytoskeleton
Volume:
78
Issue:
6
ISSN:
1949-3584
Page Range / eLocation ID:
p. 303-311
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. Summary

    Actin filament assembly in plants is a dynamic process, requiring the activity of more than 75 actin‐binding proteins. Central to the regulation of filament assembly and stability is the activity of a conserved family of actin‐depolymerizing factors (ADFs), whose primarily function is to regulate the severing and depolymerization of actin filaments. In recent years, the activity ofADFproteins has been linked to a variety of cellular processes, including those associated with response to stress. Herein, a wheatADFgene,TaADF4,was identified and characterized.TaADF4encodes a 139‐amino‐acid protein containing five F‐actin‐binding sites and two G‐actin‐binding sites, and interacts with wheat (Triticum aestivum) Actin1 (TaACT1),in planta. Following treatment of wheat, separately, with jasmonic acid, abscisic acid or with the avirulent race,CYR23, of the stripe rust pathogenPuccinia striiformisf. sp.tritici, we observed a rapid induction in accumulation ofTaADF4mRNA. Interestingly, accumulation ofTaADF4mRNAwas diminished in response to inoculation with a virulent race,CYR31. Silencing ofTaADF4resulted in enhanced susceptibility toCYR23, demonstrating a role forTaADF4in defense signaling. Using a pharmacological‐based approach, coupled with an analysis of host response to pathogen infection, we observed that treatment of plants with the actin‐modifying agent latrunculin B enhanced resistance toCYR23, including increased production of reactive oxygen species and enhancement of localized hypersensitive cell death. Taken together, these data support the hypothesis thatTaADF4 positively modulates plant immunity in wheat via the modulation of actin cytoskeletal organization.

     
    more » « less
  2. Abstract

    The actin‐related protein 2/3 complex (Arp2/3 complex), a key regulator of actin cytoskeletal dynamics, has been linked to multiple cellular processes, including those associated with response to stress. Herein, theSolanum habrochaitesARPC3gene, encoding a subunit protein of the Arp2/3 complex, was identified and characterized.ShARPC3encodes a 174‐amino acid protein possessing a conserved P21‐Arc domain. Silencing ofShARPC3resulted in enhanced susceptibility to the powdery mildew pathogenOidium neolycopersici(On‐Lz), demonstrating a role forShARPC3in defence signalling. Interestingly, a loss ofShARPC3coincided with enhanced susceptibility toOn‐Lz, a process that we hypothesize is the result of a block in the activity of SA‐mediated defence signalling. Conversely, overexpression ofShARPC3inArabidopsis thaliana, followed by inoculation withOn‐Lz, showed enhanced resistance, including the rapid induction of hypersensitive cell death and the generation of reactive oxygen. Heterologous expression ofShARPC3in thearc18mutant ofSaccharomyces cerevisiae(i.e.,∆arc18) resulted in complementation of stress‐induced phenotypes, including high‐temperature tolerance. Taken together, these data support a role for ShARPC3 in tomato through positive regulation of plant immunity in response toOneolycopersicipathogenesis.

     
    more » « less
  3. Abstract

    We describe sloth assemblages from theCocinetasBasin (LaGuajira peninsula,Colombia), found in theNeogeneCastilletes andWare formations, located in northernmostSouthAmerica, documenting otherwise poorly known biotas. The tentative referral of a specimen to a small megatherioid sloth,Hyperleptus?, from the early–middleMioceneCastilletesFormation, suggests affinities of this fauna with the distantSantaCruzFormation and documents a large latitudinal distribution for this taxon. The latePlioceneWareFormation is much more diverse, with five distinct taxa representing every family of ‘ground sloths’. This diversity is also remarkable at the ecological level, with sloths spanning over two orders of magnitude of body mass and probably having different feeding strategies. Being only a few hundred kilometres away from theIsthmus ofPanama, and a few hundred thousand years older than the classically recognized first main pulse of theGreatAmericanBiotic interchange (GABI1), theWareFormation furthermore documents an important fauna for the understanding of this major event inNeogene palaeobiogeography. The sloths for which unambiguous affinities were recovered are not closely related to the early immigrants found inNorthAmerica beforeGABI1.

     
    more » « less
  4. Abstract

    Steep genetic clines resulting from recent secondary contact between previously isolated taxa can either gradually erode over time or be stabilized by factors such as ecological selection or selection against hybrids. We used patterns of variation in 30 nuclear and two mitochondrialSNPs to examine the factors that could be involved in stabilizing clines across a hybrid zone between two subspecies of the Atlantic killifish,Fundulus heteroclitus. Increased heterozygote deficit and cytonuclear disequilibrium in populations near the center of the mtDNAcline suggest that some form of reproductive isolation such as assortative mating or selection against hybrids may be acting in this hybrid zone. However, only a small number of loci exhibited these signatures, suggesting locus‐specific, rather than genomewide, factors. Fourteen of the 32 loci surveyed had cline widths inconsistent with neutral expectations, with twoSNPs in the mitochondrial genome exhibiting the steepest clines. Seven of the 12 putatively non‐neutral nuclear clines were forSNPs in genes related to oxidative metabolism. Among these putatively non‐neutral nuclear clines,SNPs in two nuclear‐encoded mitochondrial genes (SLC25A3 andHDDC2), as well asSNPs in the myoglobin, 40S ribosomal protein S17, and actin‐bindingLIMprotein genes, had clines that were coincident and concordant with the mitochondrial clines. When hybrid index was calculated using this subset of loci, the frequency distribution of hybrid indices for a population located at the mtDNAcline center was non‐unimodal, suggesting selection against advanced‐generation hybrids, possibly due to effects on processes involved in oxidative metabolism.

     
    more » « less
  5. Summary

    Phagocytosis, macropinocytosis and antigen presentation by dendritic cells (DC) requires reorganization of the actin cytoskeleton. Drebrin (Dbn1) is an actin binding and stabilizing protein with roles in endocytosis, formation of dendrite spines in neurons and coordinating cell–cell synapses in immune cells. However, its role inDCphagocytosis and antigen presentation is unknown. These studies now report that silencing of Dbn1 inDCresulted in restrained cell surface display of receptors, most notablyMHCclass I andIIand co‐stimulatory molecules. This, as expected, resulted in impaired antigen‐specific T‐cell activation and proliferation. Studies additionally revealed that knockdown of Dbn1 inDCimpaired macropinocytosis and phagocytosis. However, there was a concomitant increase in fluid‐phase uptake, suggesting that Dbn1 is responsible for the differential control of macropinocytosis versus micropinocytosis activities. Taken together, these findings now reveal that Dbn1 plays a major role in coordinating the actin cytoskeletal activities responsible for antigen presentation inDC.

     
    more » « less