Sally Twining, Ph.D.

Professor

Dr. Twining received her Doctorate degree in Physiological Chemistry from Ohio State University. She did postdoctoral work at the Mayo Clinic in immunochemistry and at the Medical College of Wisconsin in proteinase activation. 

Contact Information

Phone: (414) 955-8431
Fax: (414) 955-6510
Email: stwining@mcw.edu

Research Interests

The two major projects in the laboratory are 1) elucidation of the role of proteinases and proteinase inhibitors in corneal wound healing and corneal ulceration and 2) exploration of the effects of maspin in corneal wound healing and in carcinogenesis.
 

The cornea has two major functions; refraction of light and protection of the eye. Retention of the avascularity and transparency of the cornea is crucial for vision. Understanding the mechanism of normal and abnormal corneal wound healing is important because of the approximately 1 million refractive surgeries such
as LASIK performed each year in the US. Upon wounding, the external barrier of the cornea is reassembled through the movement of the epithelial cells from the non-injured regions of the cornea followed by cell division and stratification of the epithelial layer. In the stroma, the cells near the injury undergo apoptosis. Cells more distant from the wound divide and undergo a phenotypic change to form mobile fibroblasts and with time the formation of contractile myofibroblasts. The fibroblasts and myofibroblasts remodel the stromal area of apoptosis. With time this area is repopulated with the quiescent normal keratocytes. In humans, this process can continue for at least 7-10 years.

Our previous work showed that prothrombin, the precursor of the coagulation protease thrombin, is both found within corneal epithelial, stromal and endothelial cells and associated with the extracellular matrix of the stroma. Not only is prothrombin present but also its mRNA. In addition to prothrombin, the message and protein for the other coagulation factors of the intrinsic and extrinsic pathways are found in the cornea. During wound healing, cornea synthesized thrombin, the last protease of the coagulation pathway, is activated by coagulation factors synthesized by the corneal epithelial and stromal cells. Fibrinogen is converted to fibrin and deposited on the surface of the injured cornea and within the stromal matrix. The roles of thrombin, in addition to cleavage of fibrinogen to fibrin, in corneal wound healing are being explored. One of these is cleavage of protease activated receptors, PARs, revealing a cryptic ligand. Upon binding this ligand to the PAR binding site, multiple signaling pathways are activated. These pathways can regulate processes such as cell proliferation, adhesion and migration and can modify gene expression. The effect of thrombin on proteases in the plasminogen activator system, members of the CCN family of proteins, Cyr61 and CTGF, as well as, other growth factors and chemokines are being explored in corneal cells.

One of the major causes of corneal ulceration is bacterial keratitis. Bacteria invasion of host tissues requires proteases that degrade host tissues. Pseudomonas aeruginosa is of specific concern because it colonizes on soft contact lenses. This organism produces a number of secreted factors that alter host functions including the protease Pseudomonas elastase. There are two forms of this enzyme but the functional implications of these differences are not known and are the focus of our studies.

Maspin is a non-inhibitory member of the Serpin (SERpin Protease INhibitor) family which is synthesized by epithelial and endothelial cells and stromal keratocytes in the normal cornea. It stimulates adhesion of cells to extracellular matrix molecules and inhibits migration and invasion of cells including corneal stromal fibroblasts and carcinoma cells. In addition, maspin inhibits angiogenesis though inhibition of vascular endothelial cell proliferation and migration. Our previous work showed that the reactive site loop peptide is sufficient for stimulation of adhesion, inhibition of migration and invasion. Our model of maspin function in the cornea includes regulation of migration of corneal cells through downregulation of maspin synthesis in the stromal fibroblast and myofibroblast phenotypes which allows migration of these cells into the wounded area. Downregulation of maspin synthesis by stromal fibroblasts and myofibroblasts involves DNA and histone methylation in the CpG islands in the promoter. We hypothesize that maspin released by the intact epithelial layer above the wounded cornea inhibits migration of the cells as they repopulate the wounded area. Corneal epithelial cells release maspin through non-classical mechanisms; exosomes and cell death. This released maspin is post-translationally phosphorylated at one or more of eight serine and threonine residues. The functional implications of phosphorylation of maspin is being explored as well as characterization of the locations of phosphorylation on intracellular maspin.
   

Selected Publications

"Identification of phosphorylation sites on extracellular corneal epithelial cell maspin." Narayan M, Mirza SP, Twining SS. Proteomics. 2011, 11(8):1382-90

"Maspin: the molecular bridge between the plasminogen activator system and {beta}1 integrin that facilitates cell adhesion." Endsley MP, Hu Y, Deng Y, He X, Warejcka DJ, Twining SS, Gonias SL, Zhang M. J Biol Chem. 2011 May 23. [Epub ahead of print]

“PepD participates in the mycobacterial stress response mediated through MprAB and SigE.” White MJ, He H, Penoske RM, Twining SS, Zahrt TC. J Bacteriol. 192(6):1498-510 (2010)

“Residues essential for plasminogen binding by the cation-independent mannose 6-phosphate receptor.” Bohnsack RN, Patel M, Olson LJ, Twining SS, Dahms NM. Biochemistry. 49(3):635-44 (2010)

“Focus on molecules: maspin.” Narayan M, Twining S. Exp Eye Res. 90(1):2-3(2010)
 
“Epigenetic silencing of maspin expression occurs early in the conversion of keratocytes to fibroblasts.” Horswill MA, Narayan M, Warejcka DJ, Cirillo LA, Twining SS. Exp Eye Res. 86(4):586-600 (2010)

"Regulation of the Urokinase Pathway by Corneal Fibroblasts and Myofibroblasts." A.M. Bernstein, S.S. Twining, D.J. Warejcka, E. Tall, and S.K. Masur. Mol. Biol. Cell, 18, 2716-2727 (2007)

"Corneal activation of prothrombin to thrombin independent of vascular injury." A. Ayala, D.J. Warejcka, M. Olague-Marchan and S.S. Twining. Invest. Ophthalmol. Vis. Sci., 48, 134-143 (2007)

"Differential conversion of plasminogen to angiostatin by human corneal cell populations." D.J. Warejcka, K.A. Vaughan, A.M. Bernstein and S.S. Twining.  Mol. Vis. 47, 859-868 (2005)

"The Fibrinolysis Inhibitor alpha2-Antiplasmin in the human Cornea." A. Ayala, D.J. Warejcka, K. Vaughan, BYJT Yue and S.S. Twining. Curr. Eye Res. 1097-1103 (2005)

"Specific conformational changes of plasminogen induced by chloride ions, 6-aminohexanoic acid and benzamidine but not the overall openness of plasminogen regulate production of biologically active angiostatins." D.J. Warejcka and S.S. Twining. Biochem. J., 392, 703-712 (2005)

"Identification of a Novel Secreted Protease from Pseudomonas aeruginosa that Causes Corneal Erosions." M.E. Marquart, A.R. Caballero, M. Chomnawang, B.A. Thibodeaux, S.S. Twining, R.J. O'Callaghan. Invest. Ophthalmol. Vis. Sci., 46(10):3761-3768 (2005)

"The effects of sub-solar levels of UV-A and UV-B on rabbit corneal and lens epithelial cells." C.S. Rogers, L.M. Chan, Y.S. Sims, K.D. Byrd, D.L. Hinton and S.S. Twining. Exp. Eye Res., 78(5):1007-1014 (2004)

"Mutation of lasA and lasB reduces Pseudomonas aeruginosa invasion of epithelial cells."B.A. Cowell, S.S. Twining, J.A. Hobden, M.S. Kwong and S.M. Fleiszig. Microbiology, 149(Pt 8):2291-2299 (2003)

"Sufficiency of the reactive site loop of maspin for induction of cell-matrix adhesion and inhibition of cell invasion. Conversion of ovalbumin to a maspin-like molecule." C. Ngamkitidechakul, D.J. Warejcka, J.M. Burke, W.J. O'Brien and S.S. Twining. J. Biol. Chem., 278(34): 31796-31806 (2003)

"Buffered non-fermenter system for lab-scale production of secreted recombinant His-tagged proteins in Saccharomyces cerevisiae." C. Ngamkitidechakul and S.S. Twining. Biotechniques., 33(6): 1296-1300 (2002)

"Functional characterization of arginine 30, lysine 40, and arginine 62 in Tn5 transposase." S.S. Twining, I.Y. Goryshin, A. Bhasin, W.S. Reznikoff. J. Biol. Chem., 276(25): 23135-23143 (2001)

"Maspin: synthesis by human cornea and regulation of in vitro stromal cell adhesion to extracellular matrix." C. Ngamkitidechakul, J.M. Burke, W.J. O'Brien, S.S. Twining. Invest. Ophthalmol. Vis. Sci., 42(13): 3135-41(2001)

"A critical role for neutrophil elastase in experimental bullous pemphigoid." Z. Liu, S.D. Shapiro, X. Zhou, S.S. Twining, R.M. Senior, G.J. Giudice, J.A. Fairley, L.A. Diaz. J. Clin. Invest., 105(1): 113-123 (2000)

"Blood glucose laboratory for first-year medical students: an interdisciplinary model for nutrition-focused diabetes management." S.A. Reiter, C.R. McGill, S.L. Lawrence, S.S. Twining. J. Am. Diet Assoc., 100(5): 570-572 (2000)

"A disease-associated glycine substitution in BP180 (type XVII collagen) leads to a local destabilization of the major collagen triple helix." M. Olague-Marchan, S.S. Twining, M.K. Hacker, J.A. McGrath, L.A. Diaz, G.J. Giudice. Matrix Biol., 19(3): 223-233 (2000)

"The serpin alpha1-proteinase inhibitor is a critical substrate for gelatinase B/MMP-9 in vivo." Z. Liu, X. Zhou, S.D. Shapiro, J.M. Shipley, S.S. Twining, L.A. Diaz, R.M. Senior, Z. Werb. Cell, 102(5): 647-655 (2000)

Extrahepatic synthesis of plasminogen in the human cornea is up-regulated by interleukins-1alpha and -1beta. S.S. Twining, P.M. Wilson, and C. Ngamkitdaichakul. Biochem. J., 339: 705-712 (1999)

"Tn5: A molecular window on transposition." W.S. Reznikoff, A. Bhasin, D.R. Davies, I.Y. Goryshin, L.A. Mahnke, T. Naumann, I. Rayment, M. Steiniger-White, S.S. Twining. Biochem. Biophys. Res. Commun., 266(3): 729-734 (1999)

Involvement of Sp1 elements in the promoter activity of the alpha1-proteinase inhibitor gene. Y. Li, L. Zhou, S.S. Twining, J. Sugar, and B.Y.T. Yue. J. Biol. Chem., 273: 9959-9965 (1998)

"Local control of alpha1-proteinase inhibitor levels: regulation of alpha1-proteinase inhibitor in the human cornea by growth factors and cytokines." G. Boskovic, S.S. Twining. Biochim. Biophys. Acta., 1403(1): 37-46 (1998)

"Changes in Rat Corneal Matrix Metalloproteinases and Serine Proteinases under Vitamin A Deficiency." S.S. Twining, D.P. Schulte, P.M. Wilson, B. Fish and J. Moulder. Curr. Eye Res., 16: 156-165 (1997)

Retinol and retinaldehyde specifically increase alpha1-proteinase inhibitor in the human cornea G. Boskovic and S.S. Twining. Biochem. J., 322: 751-756 (1997)