Hemophilia A, the most common of the severe, inherited bleeding disorders, results from a deficiency or defect in the plasma protein, factor VIII. There is no cure for hemophilia A and treatment consists of replacement therapy using preparations of the (purified) protein. During the last funding period the applicant has made significant strides in identifying and characterizing sequences and ligands important for factor VIII/factor VIIIa subunit structure and function. The applicant will use this information as a platform for study, applying physical and biochemical approaches and utilizing molecular biological methods, to elucidate fine point structural details of intra-protein interactions that will define mechanisms for the regulation of this critical plasma protein.
The first aim will study the relatively the weak affinity interaction between the Al and A2 subunits in factor VIIIa which governs subunit structure and function of the active protein. The goal is to identify and determine the roles of residues that participate in this inter-subunit interaction. To this end the applicant will (i) use zero-length cross-linking to identify interactive residues, (ii) construct and analyze point mutations in factor VIII and subunits to assess these interactions, (iii) examine the role of critical histidine residues in the Ph-dependent association of the subunits, (iv) evaluate naturally occurring inhibitors in the inter-subunit interaction, (v) examine changes in A2 conformation upon its binding to the primary interactive site in Al and (vi) probe for interactions independent of that site.
The second aim studies interactions between factor VIII light chain and heavy chain. The goal is to define and model the association of these two chains. Proposed studies will (i) compare Ca(II) and Mn(II) as effectors of reconstitution and determine their influence on subunit structure and conformation, (ii) characterize Me2+-independent interactions of the heavy and light chains, and (iii) model the association of the subunits.The underlying theme of this program is to identify sequences and mechanisms responsible for the integrity and stability of molecular structure. Definition of these issues will yield valuable insights into the biochemistry of the native as well as dysfunctional factor VIII molecules, and provide information for the design of superior therapeutics.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL038199-14
Application #
6389027
Study Section
Hematology Subcommittee 2 (HEM)
Program Officer
Link, Rebecca P
Project Start
1988-04-01
Project End
2002-03-31
Budget Start
2001-04-01
Budget End
2002-03-31
Support Year
14
Fiscal Year
2001
Total Cost
$245,198
Indirect Cost
Name
University of Rochester
Department
Internal Medicine/Medicine
Type
Schools of Dentistry
DUNS #
208469486
City
Rochester
State
NY
Country
United States
Zip Code
14627
Monaghan, M; Wakabayashi, H; Griffiths, A E et al. (2016) Stabilizing interactions between D666-S1787 and T657-Y1792 at the A2-A3 interface support factor VIIIa stability in the blood clotting pathway. J Thromb Haemost 14:1021-30
Leong, Lilley; Sim, Derek; Patel, Chandra et al. (2015) Noncovalent stabilization of the factor VIII A2 domain enhances efficacy in hemophilia A mouse vascular injury models. Blood 125:392-8
Monaghan, M; Wakabayashi, H; Griffiths, A et al. (2014) Enhanced factor VIIIa stability of A2 domain interface variants results from an increased apparent affinity for the A2 subunit. Results from an increased apparent affinity for the A2 subunit. Thromb Haemost 112:495-502
Kosloski, Matthew P; Shetty, Krithika A; Wakabayashi, Hironao et al. (2014) Effects of replacement of factor VIII amino acids Asp519 and Glu665 with Val on plasma survival and efficacy in vivo. AAPS J 16:1038-45
Wakabayashi, Hironao; Monaghan, Morgan; Fay, Philip J (2014) Cofactor activity in factor VIIIa of the blood clotting pathway is stabilized by an interdomain bond between His281 and Ser524 formed in factor VIII. J Biol Chem 289:14020-9
Wakabayashi, H; Wintermute, J M; Fay, P J (2014) Combining mutations that modulate inter-subunit interactions and proteolytic inactivation enhance the stability of factor VIIIa. Thromb Haemost 112:43-52
Wakabayashi, Hironao; Fay, Philip J (2013) Replacing the factor VIII C1 domain with a second C2 domain reduces factor VIII stability and affinity for factor IXa. J Biol Chem 288:31289-97
Wakabayashi, Hironao; Fay, Philip J (2013) Molecular orientation of factor VIIIa on the phospholipid membrane surface determined by fluorescence resonance energy transfer. Biochem J 452:293-301
Takeyama, Masahiro; Wakabayashi, Hironao; Fay, Philip J (2013) Contribution of factor VIII light-chain residues 2007-2016 to an activated protein C-interactive site. Thromb Haemost 109:187-98
Griffiths, Amy E; Rydkin, Ivan; Fay, Philip J (2013) Factor VIIIa A2 subunit shows a high affinity interaction with factor IXa: contribution of A2 subunit residues 707-714 to the interaction with factor IXa. J Biol Chem 288:15057-64

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