C. Andrew Powers, Ph.D.
Associate Professor of Pharmacology
Department of Pharmacology
Basic Sciences Building
New York Medical College
Valhalla, NY 10595
Glandular kallikrein (GK) is a trypsin-like protease classically characterized by its ability to generate bioactive peptides (kinins) from large inactive precursor proteins (kininogens). Investigation of the potential role of GK in prohormone processing led to its discovery in the anterior pituitary where it is highly induced by estrogens and repressed by dopamine in lactotrophs - cells that secrete prolactin (PRL). A novel thiol-dependent processing reaction was discovered which enabled GK to cleave 3 highly conserved sites in the C-terminus of PRL to generate a large N-terminal fragment (174 a.a.), and 3 smaller peptides (11, 3, and 9 a.a.). The pituitary was found to secrete a novel estrogen- and thiol-dependent PRL product (PRL1-173) produced via serial processing by GK and carboxypeptidase E. The biological significance of this highly regulated and unusual processing remains a mystery.
Another research interest concerned the role of hormonal interplay with thyroid hormone in the integrative physiological mechanisms involved in the effects of estrogens and antiestrogens (such as tamoxifen) on energy balance, bone and lipid metabolism, growth and cardiovascular function in rat models relevant to human physiology and pathophysiology. The work indicates that estrogen and antiestrogen modulation of the actions and/or secretion of thyroid hormone, growth hormone (GH) and insulin-like growth factor I (IGF-I) contributes to estrogen and tamoxifen effects on a diverse subset of estrogen targets. Conversely, changes in the functional status of the thyroid or GH-IGF-I axis may alter the effects of estrogens and antiestrogens on such targets. The research may provide insights relevant to novel therapeutic uses for antiestrogens.
Post Graduate Studies
Graduate Degree: Ph.D.
Graduate Degree Institution: University of Kansas
Undergraduate Institution: Eckerd College
Fitts JM, Klein RM and Powers CA (2004) Comparison of tamoxifen and testosterone propionate in male rats: differential reversal of orchidectomy effects on sex organs, growth, bone mass and the growth hormone-IGF-I axis. J Andrology 25:523-534.
Fitts JM, Klein RM and Powers CA (2001) Estrogen and tamoxifen interplay with T3 in male rats: pharmacologically distinct classes of estrogen responses affecting growth, bone and lipid metabolism, and their relation to serum GH and IGF-I. Endocrinology 142: 4223-4235.
Powers CA (1993) Anterior pituitary glandular kallikrein: a putative prolactin processing protease. Mol Cell Endocrinol 90:C15-C20. (review article).
Anthony PK, Stoltz RA, Pucci ML, Powers CA (1993) The 22K variant of rat prolactin: evidence for identity to prolactin-(1-173), storage in secretory granules, and regulated release. Endocrinology 132:806-814.
Powers CA, Hatala MA (1986) Dopaminergic regulation of the estrogen-induced glandular kallikrein in the rat anterior pituitary. Neuroendocrinology 44:462-469.