Fibrinogen and Factor XIII Prof. John W. Weisel

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1 Fibrinogen and Factor XIII John W. Weisel Dept. of Cell & Developmental Biology University of Pennsylvania School of Medicine Philadelphia, PA USA The screen versions of these slides have full details of copyright and acknowledgements 1

2 4 5 6 The screen versions of these slides have full details of copyright and acknowledgements 2

3 Biosynthesis of fibrinogen Three fibrinogen genes located on chromosome 4 Aα chain - 5 exons; 1-2% αe extended chain Bβ chain - 8 exons; Transcribed opposite direction γ chain - 10 exons; 10-15% γ alternately spliced g liver synthesis/day; 3-5 day half life Single chain to two chain to three chain half molecules that dimerize Post-translational modifications The screen versions of these slides have full details of copyright and acknowledgements 3

4 10 Schematic model of complementary binding sites 11 Litvinov et al. Blood (2005) 106, Activation of factor XIII 12 The screen versions of these slides have full details of copyright and acknowledgements 4

5 13 Factor XIIIa stabilizes fibrin The carboxyl terminal ends of fibrin s γ chains are crosslinked more rapidly Multiple sites in the carboxyl terminal end of the α chains are crosslinked The screen versions of these slides have full details of copyright and acknowledgements 5

6 16 17 Weisel et al., PNAS 84, 8991, The screen versions of these slides have full details of copyright and acknowledgements 6

7 Weisel, Biophys. Chem. 112, 267, Weisel, Biophys. Chem. 112, 267, Weisel, Biophys. Chem. 112, 267, The screen versions of these slides have full details of copyright and acknowledgements 7

8 Fraction of each structure shown 22 Fibrin is a viscoelastic polymer Elastic material (e.g., superball): strain (deformation) proportional to stress (force/area) (Hooke s law) Viscous material (e.g., clay): stress proportional to the rate of strain (Newton s law) 23 The unique mechanical properties of fibrin arise even though the protein in a typical plasma clot (2.5 g/l fibrinogen) constitutes only 0.25% of the mass; 99.75% is liquid 24 The screen versions of these slides have full details of copyright and acknowledgements 8

9 Fibrin clot formation: turbidity curves 25 (Based on Roberts, et al., Biorheol. 10, 29, 1973) 26 (Roberts, et al., Biorheol. 10, 29, ) The screen versions of these slides have full details of copyright and acknowledgements 9

10 Binding of other proteins to fibrin(ogen) Albumin Fibronectin Thrombospondin Von Willebrand factor Fibulin Growth factors 28 Weisel, Biophys. Chem. 112, 267, Weisel, Adv. Prot. Chem. 70, 247, The screen versions of these slides have full details of copyright and acknowledgements 10

11 t-pa catalyzed plasminogen activation & fibrin clot lysis 31 Fragments from plasmin digestion of fibrin The screen versions of these slides have full details of copyright and acknowledgements 11

12 The screen versions of these slides have full details of copyright and acknowledgements 12

13 37 Transmission electron microscope images of rotary shadowed α IIb β 3 A B C D 38 Electron microscope images of fibrinogen-integrin complexes 39 The screen versions of these slides have full details of copyright and acknowledgements 13

14 40 Dysfibrinogenemias Single base mutation - single amino acid substitution, addition, deletion, or stop codon May be thrombotic, hemorrhagic or asymptomatic Some mutations may give rise to congenital hypo or afibrinogenemia Important for the insights that they give into fibrinogen functions 41 Fibrinogen variants More than a million non-identical forms in an individual AαThr312Ala; BβArg448Lys Carbohydrate Splice variants Serine phosphorylation Proline hydroxylation Tyrosine sulfation or nitration Asparagine or glutamine deamidation Glutamine cyclization Methionine oxidation Lysine glycation Proteolytic degradation 42 The screen versions of these slides have full details of copyright and acknowledgements 14

15 Evolution of fibrinogen Present in all vertebrates Three chains homologous, indicating that they evolved from a common ancestor Sequence comparisons imply that fibrinogen evolved before the divergence of vertebrates and invertebrates Fibrinogen-like sequences have been identified in invertebrates and in some other proteins The existence of these fibrinogen-like domains suggests that these specific and tightly controlled interactions may be used in other aspects of cell and developmental biology The screen versions of these slides have full details of copyright and acknowledgements 15