Principles of Biochemistry 6 |Blood Coagulation| Class Notes |HarvardX

Blood Clot

Initiation

• Von Willebrand factor attaches to the collagen fibers.
• unfolding of the fiber and expose the bind sites of the vWWF
• attach the surface of the platelets
• platelets started to attach the lesion site.

Extension

consistant the recruitment of addition platelets.
It was contributed by the fibrinogen, which has two binding sites for intergins.

The release of ADP and thromboxane A2 by activate platelets attached.
-> soft plug

Stabilization

Conversion of fibrinogen into fibrin and the polymerization of the fibrin into a network of fibers.
Stabilize anchored by thrombin.

Four molecules:

• collagen
• Thrombin: initiate
• ADP/TxA: initiate pyhsical respons
• platelets shell

Fibrinogen

The third most abundant protein in blood plasma, consisting of two C-terminal domains.

From fibrinogen to fibrin:

• controlled by the activation of the thrombin.
• cleave a small portion (18~20) to release 2 binding sites.
• binding sites could react with other fibrin’s C-terminal
• turned into a meshwork of fibers.
• meshwork extended from the base of the platelet plug into the lesion
• which tenses the platelet plug

A positive feedback process

© Wayne W. LaMorte; 2016

As shown above, the blood vessel has a few layers. Surrounding the endothelium, cells in the second layer of the vessel are characterized by expression tissue factors that could trigger blood coagulation.

The lesion would expose the second layer and release the tissue factors.

Two pathway of the coagulation cascade

• Extrinsic (first)
• Intrinsic: activated plates.

Two pathway of the coagulation cascade

Extrinsic

VII: coagulation factor VII
VII_a: activated coagulation factor VII
TF + VII -> TF - VII_a (composite)
VII_a: IX -> IX_a
IX_a: X -> X_a
X_a + V_a + TF
X_a + V_a + TF: pro-thrombin -> thrombin
thrombin: fibrinogen -> fibrin

thrombin: V_a
trhombin -> VIII_a
VIII_a: X -> X_a
thrombin: XIII_a
XIII_a: polymerization

Intrinsic path

Initiated when some hazer or foreign be recognized.

XII -> XII_a
XII_a: XI -> XI_a
like above.

Misbehavior of the Intrinsic pathway could cause blood clots to cause disease.

The stop of the coagulation

Thrombin: control the size of the blood clot.

Thrombin + Protein S complexes -> bind to thrombomodulin: form a ternary complex

ternary complex -> Protein C
Protein C: Inactivation of IX and X to stop the clot.

Two additional levels of inhibition:

1. TFPIa binds and inactivates the ternary complexes (TF, VIIa, and Xa)
2. Antithrombin 3 binds irreversibly to thrombin. It also responds to the inactivation of the IX, X, XI, and XII.

Thrombus Detection

Thrombus

© Peter Caravan, Ph.D.

• Blood clot that forms in the arteries or veins of the body
• Can cause stroke, coronary artery disease, pulmonary embolism, deep vein thrombosis
• Affects millions of people and costs billions of dollars worldwide.
• Developing new imaging tools is essential for diagnosis and monitoring disease progression

Fibrin imaging

• Fibrin is an attractive target for thrombus image
  • only present in blood clots and wound hearling
  • not found in circulating blood
• High density for disease, no background.

Phage Display

1. Phage library filter:
   • incubate the phage with fibrin and collect the phage which bind with it.
2. Phage proliferation:
   • Incubate the phage with E. coli to proliferate them.
3. Improve the affinity:
   • Repeat the phase 1 and 2 over and over again.
4. Characterize those phage
5. Magnetic Resonance Imaging (MRI)
   • Need large magnetic field and radiofrequency energy for detection

Magnetic Resonance Imaging (MRI)

1. It is able to detect the Hydrogen molecules and mobile molecules, which are mainly water and fats.
2. Metal is another important resource, Gadolinium ion, especially.

© pubchem:24847884	© Penka A Atanassova

• Label with radioactive isotope
  • Positron Emission Tomography
• Label with fluorescent dye
  • Fluorescent microscopy
• Label with EP-2014R:
  • Fibrin-binding peptide coupled to 4 Gadolinium chelates.
  • Binds reversibly and specifically to fibrin
  • Low affinity for fibrinogen, albumin and other components of plasma
  • High relaxivity: makes clots bright.

digraph F { rankdir = "LR" subgraph cluster_0{ label = "Human Blood Clot" Platelets Fibrin Platelets -> Platelets_E Fibrin -> Fibrin_E subgraph A { rank = 1 Fibrin Fibrin_E } subgraph B { rank = 2 Platelets Platelets_E } Platelets_E [shape = box, label= "form a soft plug"] Fibrin_E [shape = box, label = "fibrous protein forms a mesh"] } }digraph F { rankdir = "LR" subgraph cluster_1{ node [shape= none] label ="Three Phases of Blood Coagulation" Initiation [label = "1. Initiation"] Extension [label = "2. Extension"] Stabilization [label = "3. Stabilization"] Cascade [label = "Coagulation Cascade", fontcolor = "red"] } subgraph cluster_2 { node [shape = box] In_1 [label = "Von Willebrand factor (vWF) attaches to the collagen fibers."] In_2 [label = "unfolding of the fiber and expose the bind sites of the vWF"] In_3 [label = "attach the surface of the platelets"] In_4 [label = "platelets started to attach the lesion site"] label = "Initiation" In_1 -> In_2 -> In_3 -> In_4 subgraph A { rank = same In_4 In_3 In_2 In_1 } } Initiation -> In_1 subgraph cluster_3 { label = "Extension" Extension_1 [shape = none, label = "Consistant the recruitment of addition platelets. It was contributed by the fibrinogen, which has two binding sites for intergins. The release of ADP and thromboxane A2 by activate platelets attached. to form a soft plug"] } Extension -> Extension_1 subgraph cluster_4 { label = "Stabilization" Stabilization_Ex [shape = none, label = "Conversion of fibrinogen into fibrin and the polymerization of the fibrin into a network of fibers"] subgraph cluster_4_1{ node [shape =underline] ssub1 [label = "1. collagen"] ssub2 [label = "2. Thrombin: initiate"] ssub3 [label = "3. ADP/TxA: \n initiate pyhsical respons"] ssub4 [laebl = "5. Platelets Shell"] label = "Four molecules" fontcolor = "blue" } } Stabilization -> ssub1 }digraph F { "marr0001" [shape=diamond,style=filled,label="",height=.1,width=.1] ; "marr0002" [shape=diamond,style=filled,label="",height=.1,width=.1] ; "marr0003" [shape=diamond,style=filled,label="",height=.1,width=.1] ; "marr0004" [shape=diamond,style=filled,label="",height=.1,width=.1] ; "marr0005" [shape=diamond,style=filled,label="",height=.1,width=.1] ; "marr0006" [shape=diamond,style=filled,label="",height=.1,width=.1] ; "marr0007" [shape=diamond,style=filled,label="",height=.1,width=.1] ; "marr0008" [shape=diamond,style=filled,label="",height=.1,width=.1] ; "marr0009" [shape=diamond,style=filled,label="",height=.1,width=.1] ; TF [label ="tissue factor"] TF_VII [label = "{<f2>Xa|<f3>Va}|{<f0>TF|<f1>VII}" shape = record] Pthrombin [label = "Pro-thrombin"] Polymerization [shape = box] TF -> "marr0001" VII-> "marr0001" -> TF_VII TF_VII:f0 -> marr0002 [style = dotted] IX -> marr0002 [dir = none] marr0002 -> IXa IXa -> marr0003 [style = dotted] marr0003 -> Xa X -> marr0003 [dir = none] Xa -> marr0004 -> TF_VII:f2 Va -> marr0004 -> TF_VII:f3 TF_VII:f3 -> marr0005 [style = dotted] Pthrombin -> marr0005 [dir = none] marr0005 -> thrombin thrombin -> marr0006 [style = dotted] marr0006 -> fibrin fibrinogen -> marr0006 [dir = none] thrombin -> XIIIa [style = dotted] XIIIa -> marr0007 [style = dotted] marr0007 -> Polymerization fibrin -> marr0007 [dir =none] subgraph cluster_0 { label = "Extrinsic Pathway" TF VII TF_VII IXa IX X Xa Va Pthrombin thrombin marr0001 marr0002 marr0003 marr0004 marr0005 marr0006 marr0007 fibrin fibrinogen XIIIa Polymerization fibrin } subgraph cluster_i { label = "Intrinsic Pathway" XII -> marr0008 -> XIIa XIIa -> marr0009 [style= dotted] XI -> marr0009 [dir = none] marr0009 -> XIa } XIa -> marr0002 [style = dotted] }