Susan J. Hunter

Susan J. Hunter

Executive Vice President for Academic Affairs and Provost
Degree: Ph.D. 1980 Pennsylvania State University
Phone: (207) 581-1547

Location: 201 Alumni Hall

Research Topic:
Cell biology and physiology of bone cells and developing extracellular matrix; role of growth factors in skeletal physiology

Research Program:
My laboratory is engaged in research dealing with the skeletal system, focused primarily at the biology of the osteoclast. Additionally, I am engaged in collaborative studies with other investigators dealing with the role of membrane skeleton proteins in osteoclast physiology.The osteoclast is a large, multinucleated cell that engages in the normal process of bone resorption, which is necessary for growth, repair and maintenance of a healthy skeleton. We have studied the regulation of acid production and the dynamics of the cytoskeleton in response to the major bone-acting hormones, parathyroid hormone and calcitonin. Additionally, we have investigated the effect of carbonic anhydrase inhibition on the resorptive ability of isolated osteoclasts maintained in cell culture. Our latest work deals with the membrane cytoskeletal proteins, ankyrin and spectrin, and the postulated roles they play in regulating vesicle and membrane interactions during secretion and establishing plasma membrane domains with a restricted complement of proteins.Ankyrin 1 was identified in chicken osteoclasts through cDNA library screening, sequence analysis, western blotting and immunocytochemistry. A fusion protein containing the NH2-terminal portion of glutathione-S-transferase and amino acids corresponding to the regulatory domain of chicken ankyrin 1 was used to generate an antibody. Competitive western blot analysis of isolated osteoclast fractions revealed the presence of high (~220 kd) and low (~80 kd) molecular weight isoforms of ankyrin 1. Immunocytochemistry of osteoclasts in situ showed that ankyrin was distributed throughout the cytoplasm with the heaviest deposition seen in the sealing zone adjacent to bone and a lighter deposition seen at the periphery of the nuclei and around small vacuolar structures. The results suggest that ankyrin is associated with the plasma membrane as a component of the adhesion mechanism and is also found in association with vesicle and organelle membranes.

Hunter SJ
, Gay CV, Osdoby PA, Gwynn B, Peters LL 2000. Membrane-bound and cytoplasmic isoforms of ankyrin-1 in chicken osteoclasts. Mol Biol Cell 11(supp 1):2540a.Gwynn B, Ciciotte SL, Hunter SJ, , Washburn LL, Smith RS, Andersen SG, Swank RT, Dell’Angelica EC, Bonifacino JS, Eicher EM, Peters LL 2000. Defects in the cappuccino (cno) gene on mouse chromosome 5 and human 4p cause Hermansky-udlak syndrome by an AP-3-independent mechanism. Blood 96:4227-4235.Hunter SJ, Gay CV, Osdoby PA, Peters LL 1998. Spectrin localization in Osteoclasts: Immunocytochemistry, cloning and partial sequencing. J Cell Biochem 71: 204-215.Rosen CJ, Mohan S, Hunter SJ, Vereault D, Baylink DJ 1997. Seasonal changes in bone density and in serum IGFBP-4 levels are associated with calcium intake and parathyroid hormone (PTH) concentrations in elderly New England women. J Bone Miner Res 12(suppl 1):P258.Peters LL, Gwynn B, Hunter SJ, Ciciotte SL, Eicher EM 1996. Characterization and chromosomal localization of cappuccino, a new murine platelet storage pool deficiency (SPD) mutation. Molec Biol Cell 7(suppl 1):845a.

Guillemin, G.G., S.J. Hunter, C.V. Gay 1995. Resorption of natural calcium carbonate by avian osteoclasts in vitro. Cells and Materials 5: 157-165.

Rosen, C.J., L.R. Donahue, and S.J. Hunter. 1994. Insulin-like growth factors and bone: The osteoporosis connection. Proc. Soc. Exptl. Biol. Med. 206: 83-102.

Hunter, S.J., C.J. Rosen, and C.V. Gay. 1991. In vitro resorptive activity of isolated chick osteoclasts: Effect of carbonic anhydrase inhibition. J. Bone Miner Res. 6: 61-66.