Hironao Wakabayashi, M.D., Ph.D.

Hironao Wakabayashi, M.D., Ph.D.

Contact Information

University of Rochester Medical Center
School of Medicine and Dentistry
601 Elmwood Ave, Box 712
Rochester, NY 14642

Office: (585) 273-4906

Professional Bio

Hironao Wakabayashi earned M.D. after 6 year education at Fukushima Medical School in Japan on 1988. In the Department of Pathology (II) at Fukushima Medical School he enrolled Ph.D. program. He studied on cancer invasion and metastasis and earned Ph.D. at 1992. He obtained postdoctoral training at University of Texas MD Anderson Cancer Center in Huston working on the same subject until he had an appointment as a Research Assistant Professor at The Institute for Molecular Medicine at Irvine, CA on 1996. Since 1999 he has been working as a Research Assistant Professor in the Department of Biochemistry and Biophysics at University of Rochester studying on the structural and functional analyses of blood coagulation factor VIII.

Research Bio

Structural and functional analyses of factor VIII

Factor VIII functions as a cofactor for the serine protease factor IXa in the surface-dependent conversion of zymogen factor X to the serine protease, factor Xa. Deficiency of factor VIII activity results in a marked reduction of factor IXa activity and in the subsequent rates of factor Xa generated during the propagation phase of coagulation.
My research focuses on the role of metal ions for structural integrity and function of factor VIII. Active factor VIII can be reconstituted by combining the isolated subunits in the presence of Ca2+ or Mn2+. Ca2+ had little effect on inter-subunit affinity yet converted the inactive dimer to an active form. Alternatively, Cu2+ enhanced the inter-subunit affinity ~100-fold but yielded a dimer lacking cofactor activity. Site-directed mutagenesis is employed to identify residues important in Ca2+ binding to factor VIII and resultant effects of this binding on activity. Several acidic amino acids within segment 110-126 of the A1 domain of factor VIII that likely participate in the coordination of Ca2+ necessary for generation of maximal cofactor specific activity.

Recent Publications

Wakabayashi, H., Zhou, Q., Varfaj, F., and Fay, P. J.
A3 Domain Residue Glu1829 Contributes to A2 Subunit Retention in Factor VIIIa J. Thromb. Haemost., in press.

Varfaj, F., Neuberg, J., Jenkins, P. V., Wakabayashi, H., and Fay, P. J.
Role of P1 Arg in Activated Protein C - Catalyzed Inactivation of Factor VIIIa. Biochemical J. 396, 355-362, 2006.

Wakabayashi, H., Zhou, Q., Nogami#, K., Ansong, C., Varfaj, F., Miles, S., and Fay, P. J.
pH-dependent association of factor VIII chains: Enhancement of affinity at physiological pH by Cu2+. Biochim. Biophys. Acta 1764,1094-1101, 2006.

Nogami, K., Zhou, Q., Myles, T., Leung, L. L. , Wakabayashi, H., and Fay, P. J.
Exosite-interactive Regions in the A1 and A2 Domains of Factor VIII Facilitate Thrombin-catalyzed Cleavage of Heavy Chain.
J. Biol. Chem. 280, 18476-18487, 2005.

Nogami, K., Zhou, Q., Wakabayashi, H., and Fay, P. J. Thrombin-catalyzed activation of factor VIII with His substituted for Arg372 at the P1 site.
Blood 105, 4362-4368, 2005.

Wakabayashi, H., Su, Y. C. , Ahmad, S. S. , Walsh, P. N. , and Fay, P. J.
A Glu113Ala Mutation within a Factor VIII Ca(2+)-Binding Site Enhances Cofactor Interactions in Factor Xase.
Biochemistry 44, 10298-10304, 2005.

Nogami, K., Wakabayashi, H., Ansong, C., and Fay, P. J. Localization of a pH-dependent, A2 subunit-interactive surface within the factor VIIIa A1 subunit.
Biochim. Biophys. Acta 1701, 25-35, 2004.

Nogami, K., Freas, J., Manithody, C., Wakabayashi, H., Rezaie, A. R. , and Fay, P. J.
Mechanisms of interactions of factor X and factor Xa with the acidic region in the factor VIII A1 domain.
J. Biol. Chem. 279, 33104-33113, 2004.

Nogami K., Lapan K.A., Zhou Q., Wakabayashi H., and Fay P.J.
Identification of a Factor Xa-interactive Site within Residues 337-372 of the Factor VIII Heavy Chain.
J. Biol. Chem. 279, 15763-15771, 2004.

Wakabayashi H., Freas J., Zhou Q., and Fay P.J.
Residues 110-126 in the A1 domain of factor VIII contain a Ca2+ binding site required for cofactor activity.
J. Biol. Chem. 279, 12677-12684, 2004.

Wakabayashi H., Zhen Z., Schmidt K.M., and Fay P.J.
Mn2+ binding to factor VIII Subunits and its effect on cofactor activity.
Biochemistry 42, 145-153, 2003.

Wakabayashi H., Schmidt K.M., and Fay P.J.
Ca2+ binding to both the heavy and light chains of factor VIII is required for cofactor activity.
Biochemistry 41, 8485-8492, 2002.

Wakabayashi H., Koszelak M., Mastri, M., and Fay P.J Metal-ion independent factor VIII subunit association and the role of calcium and copper for its affinity and activity.
Biochemistry 40, 10293-10300, 2001.

Recent Journal Articles

Showing the 5 most recent journal articles. 47 available »

2014 Jul 3
Wakabayashi H, Wintermute JM, Fay PJ. "Combining mutations that modulate inter-subunit interactions and proteolytic inactivation enhance the stability of factor VIIIa." Thrombosis and haemostasis.. 2014 Jul 3; 112(1):43-52. Epub 2014 Mar 06.
2014 Jun 17
Kosloski MP, Shetty KA, Wakabayashi H, Fay PJ, Balu-Iyer SV. "Effects of Replacement of Factor VIII Amino Acids Asp519 and Glu665 with Val on Plasma Survival and Efficacy In Vivo." The AAPS journal. 2014 Jun 17; Epub 2014 Jun 17.
2014 Jun 5
Monaghan M, Wakabayashi H, Griffiths A, Wintermute J, Fay PJ. "Enhanced factor VIIIa stability of A2 domain interface variants. Results from an increased apparent affinity for the A2 subunit." Thrombosis and haemostasis.. 2014 Jun 5; 112(3)Epub 2014 Jun 05.
2014 Apr 1
Wakabayashi H, Monaghan M, Fay PJ. "Cofactor Activity in Factor VIIIa of the Blood Clotting Pathway is Stabilized by an Interdomain Bond Between His 281 and Ser 524 Formed in Factor VIII." The Journal of biological chemistry.. 2014 Apr 1; Epub 2014 Apr 01.
2013 Oct 25
Wakabayashi H, Fay PJ. "Replacing the factor VIII C1 domain with a second C2 domain reduces factor VIII stability and affinity for factor IXa." The Journal of biological chemistry.. 2013 Oct 25; 288(43):31289-97. Epub 2013 Sep 12.

Current Appointments

Research Assistant Professor - Department of Biochemistry and Biophysics (SMD) - Primary


PhD | Pathology | Japan-Fukushima Med Coll1992
MD | Medicine | Japan-Fukushima Med Coll1988

Post-Doctoral Training & Residency

1992-1996 Postdoctoral Fellow, Department of Tumor Biology The University of Texas M. D. Anderson Cancer Center, Houston, Texas, U.S.A. 1996