title: Modulation of the extracellular matrix patterning of thrombospondins by actin dynamics and thrombospondin oligomer state.
abstract: Thrombospondins (TSPs) are evolutionarily-conserved, secreted glycoproteins that interact with cell surfaces and extracellular matrix (ECM) and have complex roles in cell interactions. Unlike the structural components of the ECM that form networks or fibrils, TSPs are deposited into ECM as arrays of nanoscale puncta. The cellular and molecular mechanisms for the patterning of TSPs in ECM are poorly understood. In the present study, we investigated whether the mechanisms of TSP patterning in cell-derived ECM involves actin cytoskeletal pathways or TSP oligomer state. From tests of a suite of pharmacological inhibitors of small GTPases, actomyosin-based contractility, or actin microfilament integrity and dynamics, cytochalasin D and jasplakinolide treatment of cells were identified to result in altered ECM patterning of a model TSP1 trimer. The strong effect of cytochalasin D indicated that mechanisms controlling puncta patterning depend on global F-actin dynamics. Similar spatial changes were obtained with endogenous TSPs after cytochalasin D treatment, implicating physiological relevance. Under matched experimental conditions with ectopically-expressed TSPs, the magnitude of the effect was markedly lower for pentameric TSP5 and Drosophila TSP, than for trimeric TSP1 or dimeric Ciona TSPA. To distinguish between the variables of protein sequence or oligomer state, we generated novel, chimeric pentamers of TSP1. These proteins accumulated within ECM at higher levels than TSP1 trimers, yet the effect of cytochalasin D on the spatial distribution of puncta was reduced. These findings introduce a novel concept that F-actin dynamics modulate the patterning of TSPs in ECM and that TSP oligomer state is a key determinant of this process.
authors.affiliation: School of Biochemistry, University of Bristol, Bristol BS8 1TD, U.K.
authors.forename: Andrew L
authors.initials: AL
authors.lastname: Hellewell
authors.affiliation: School of Biochemistry, University of Bristol, Bristol BS8 1TD, U.K.
authors.forename: Xianyun
authors.initials: X
authors.lastname: Gong
authors.affiliation: School of Biochemistry, University of Bristol, Bristol BS8 1TD, U.K.
authors.forename: Karsten
authors.initials: K
authors.lastname: Schärich
authors.affiliation: School of Biochemistry, University of Bristol, Bristol BS8 1TD, U.K.
authors.forename: Elena D
authors.initials: ED
authors.lastname: Christofidou
authors.affiliation: School of Biochemistry, University of Bristol, Bristol BS8 1TD, U.K. jo.adams@bristol.ac.uk.
authors.forename: Josephine C
authors.initials: JC
authors.lastname: Adams
mesh_terms: D000199:Actins / Q000378:metabolism*; D000818:Animals; D019556:COS Cells; D045744:Cell Line, Tumor; D002522:Chlorocebus aethiops; D015638:Cytochalasin D / Q000494:pharmacology; D003599:Cytoskeleton / Q000378:metabolism; D047630:Depsipeptides / Q000494:pharmacology; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism; D005109:Extracellular Matrix / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D055503:Protein Multimerization; D051381:Rats; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D019700:Thrombospondin 1 / Q000235:genetics / Q000378:metabolism; D019699:Thrombospondins / Q000235:genetics / Q000378:metabolism*
chemical_list: D000199:Actins; D047630:Depsipeptides; D029721:Drosophila Proteins; D011994:Recombinant Proteins; D019700:Thrombospondin 1; D019699:Thrombospondins; C582391:Thbs1 protein, rat; C000611726:thrombospondin-1, human; C057531:jasplakinolide; D015638:Cytochalasin D
keywords: actin; coiled-coil; cytochalasin D; extracellular matrix; jasplakinolide; thrombospondins