The section “Protein Misfolding” (leader: MFBGG) investigates the protein misfolding in physiology and disease. Protein misfolding underlies a large and increasing number of highly debilitating diseases, such as Alzheimer’s disease for which no adequate therapy is available. Our group discovered a role for the hemostatic enzymatic system termed contact system and fibrinolytic system in the protein misfolding diseases and in immunity. These findings indicate a mechanism by which the hemostatic system can control the accumulation of misfolded proteins. Hence they provide a potential therapeutic target.
Specifically, this research has focused on three research programs:
1. Identification of tPA and FXII activation by misfolded proteins.
2. Activation of blood platelets by misfolded proteins.
3. Immunogenicity of misfolded proteins and its applications.
General Aim
To elucidate the activation of biological systems by misfolded proteins, identify drug targets for misfolding diseases and develop drug leads.
1. Identification of tPA and FXII activation by misfolded proteins
We have established that both tPA and factor XII are activated by misfolded proteins and not by natively folded proteins. For factor XII this has resolved a long standing paradox and for tPA it helps to explain why it is activated and implicated in many other (patho)physiological conditions other then fibrinolysis where it was originally found to be active. The paradox that existed was the in vitro activation of coagulation by FXII due to contact of blood with artificial surfaces, but the lack of a role in physiological role in hemostasis in vivo. On the contrary, factor XII was shown to be protective for thrombotic events in epidemiological studies. We demonstrated that FXII was activated in vitro by misfolded proteins and in vivo in patients with amyloidosis (misfolding disease), leading to the formation of kallikrein, but not to the formation of XIa (coagulation). Kallikrein formation by FXII is known to occur in vivo and is implicated in may (chronic) inflammatory diseases and misfolding diseases (Alzheimer’s disease). In addition to these studies we mapped the homologous domain in tPA and factor XII and in two other proteins. We also demonstrated the presence of misfolding characteristics in fibrin, the classical tPA activator, explaining the activation of tPA by both fibrin and misfolded proteins. Finally we have demonstrated their role on the effect of misfolded proteins on (endothelial and neuronal) cell adhesion in vitro. Taken together, we have elucidated a role for these two blood born enzymatic systems. We postulate that they are part of a physiological pathway to recognize and remove misfolded proteins to prevent their accumulation and disease. We have termed this pathway the “crossbeta pathway”.
2. Activation of blood platelets by misfolded proteins.
Activation of blood platelets plays an important role in hemostasis, but may also cause unwanted obstruction of blood vessels due to the formation of intravascular clots. Most notably this can occur in the arterial vascular bed and cause heart attack or stroke. However platelet activation may also play a role in venous thrombosis. The trigger(s) underlying the trapping activation of blood platelets at sites of arterial and/or venous thrombosis are often not known. We demonstrated (1) that two components, glycated proteins and oxidized LDL that are present in vascular plaques contain properties of misfolded proteins. We also demonstrated that misfolded proteins can trigger platelet activation. This is mediated by cellular receptors, including CD36, the receptor for misfolded protein amyloid-beta that is implicated in Alzheimer’s disease. These studies may help to explain both physiological and pathological activation of blood platelets. Moreover it addresses the role of multligand receptors as receptors for proteins with common misfolded properties. Hence, we postulate that multiligand receptors are part of the aforementioned “crossbeta pathway” for the clearance of misfolded proteins.
3. Immunogenicity of misfolded proteins and their applications
Biopharmaceuticals, including therapeutic antibodies, cytokines and blood coagulation products become increasingly important in the treatment of a wide variety of diseases. While often very effective, unfortunately, they often have the a side effect of inducing an immune response against the therapeutic. This causes the treatment less efficient, but may also cause very harmfull adverse effects as has been the case with patients that developed Red Cell Aplasia because they developed anti-EPO antibodies upon treatment with a formulation of EPO. Although the presence of protein aggregates was suggested to be of importance the underlying phenomenon remained to be further elucidated. Moreover, detection of immunogenic moieties in therapeutic formulations is extremely needed according to publication from the FDA. We found that misfolded proteins in biopharmaceuticals and that their levels increased upon storage towards their expiration date. We also demonstrated that misfolding proteins comprising crossbeta structure are immunogenic. These findings are helpful in the development of tools to screen for immunogenic compositions applicable not only for improving drug safety, but also for the design of vaccines.
You can also visit: http://www.crossbeta.com
On this project are working under supervision of Dr. M.F.B.G. Gebbink and Dr. B. Bouma:
- Drs. C. Maas, Ph.D. student
- Ing. C.W. Seinen, technician
- Dr. A. Bussink, post-doc
- T. Poplonski, technician
- Vacany post-doc
Recent publications:
Maas, C, Govers-Riemslag, JWP, Bouma, B, Schiks, B, Hazenberg, B, Lokhorst, HM, Hammarström, P, ten Cate, H, de Groot, PG, Bouma, BN, Gebbink, MFBG. (2008). Factor XII is activated by misfolded proteins, which leads to kallikrein formation without initiating coagulation. J. Clin. Invest, 118, 3208-3218.
See also: Cell Biology Select, Cell 134(6), 893,895.
Maas, C, Schiks, B, Strangi, R, Hackeng, TM, Bouma, BN, Gebbink, MFBG, Bouma, B (2008). Identification of fibronectin type I domains as amyloid-binding modules on tissue-type plasminogen activator and three homologues. Amyloid 15(3), 166-180.
Herczenik, E, Gebbink, MFBG (2008). Molecular and cellular aspects of protein misfolding and disease. FASEB J. 22, 2115-2133.
Herczenik, E, Bouma, B, Korporaal, SJ, Strangi, R, Zeng, Q, Gros, P, Van Eck, M, Van Berkel, TJ, Gebbink, MFBG, Akkerman, JW (2007). Activation of human platelets by misfolded proteins. Arterioscler Thromb Vasc Biol. 27(7), 1657-1665.
Bouma, B, Maas, C, Hazenberg, BP, Lokhorst, HM, Gebbink, MFBG (2007). Increased plasmin-alpha2-antiplasmin levels indicate activation of the fibrinolytic system in systemic amyloidoses.J Thromb Haemost. 5(6):1139-1142.
Maas, C, Hermeling, S, Bouma, B, Jiskoot, W, Gebbink, MFBG. (2007). A role for protein misfolding in immunogenicity of biopharmaceuticals. J Biol Chem. 282(4): 2229-2236.