The end of the millenium and the end of the century has brought many "lists" of the best, worst, most important, etc. inventions, people, novels, discoveries, etc.

I picked five aspects of hormone discovery and application and discussed my reasons for picking them. If you want to see my justifications you will have to wait until the June issue of the journal. But here is a summary of my picks. I would be interested in your feedback, negative or positive.

1. The Pill
2. Technique of Radioimmunoassay
3. Concept of Regulation of Secretions of the Anterior Pituitary by Neurohormones
4. Identification of Hormone Receptors, Particularly Steroid Receptors
5. Discovery of Contaminating "Endocrine Disruptors", Detrimental to Animal (and Human) Reproductive Health

Remember – with a growing concern about an increasing world population and a deteriorating environment—
Reproduction matters!
—Neena Schwartz

The Department of Medicine has announced that Dr. Andrea Dunaif will become the Head of Endocrinology starting May 2001. Dr. Dunaif comes to Northwestern University after serving as Chief of the Division of Women’s Health at Brigham and Women’s Hospital, Boston. Since 1998 she has been Director of Harvard Medical School’s Center of Excellence in Women’s Health.

Dr. Dunaif received her M.D. from Columbia University College of Physicians and Surgeons. Her residency in Medicine was at Presbyterian Hospital in New York. She was a Clinical and Research Fellow in Endocrinology at Massachusetts General Hospital in 1980-81 and then a Clinical and Research Fellow in Medicine and Gynecology at the same hospital. She has published over 80 original articles and reviews and is the editor of "The Polycystic Ovary Syndrome: Endocrinology and Metabolism Clinics of North America", Vol. 28, No.2, W.B. Saunders 1999.

Dr. Dunaif will add a real presence to Northwestern University in several aspects of polycystic ovary syndrome. She has carried out research in the relation of insulin action and resistance and cardiovascular disease in women with the disease and has also been engaged in studies of possible alterations in genotypes associated with the syndrome.

Marcia L. Storch MD cholarship Fund for Undergraduate Women

CRS member V. Craig Jordan has been named the recipient of the Twenty-fourth Annual Bristol-Myers-Squibb Award for Distinguished Achivement in Cancer Research. Jordan, whose research laid the foundation for the clinical use of antiestrogens and selective estrogen receptor modulators, received the $50,000 cash prize and a silver medallion at a dinner in his honor in New York April 10. His research on tamoxifen, the estrogen antagonist, has had an impact on breast cancer treatment worldwide.

Jordan is the Diana, Princess of Wales Professor of Cancer Research and director of the Lynn Sage Breast Cancer Research Program at the Robert H. Lurie Comprehensive cancer Center of Northwestern University. He is the principal investigator on a $13 million Specialized Program of Research Excellence in Breast Cancer (SPORE) grant.

Catherine Woolley’s article in PNAS (see back page) achieved the cover of the journal (PNAS Vol. 98, #6, 2001). The picture is of a computer reconstruction of a dendrite from a hippocampal neuron.

Erv Goldberg, BMBCB, will chair the Program Committee for the 2002 American Society of Andrology Meeting.

Dan Bernard, Research Associate in the Woodruff lab, has received a Lalor Foundation Award for his project "Regulation and function of the inhibin binding protein".

Ovulation is required to propagate the species. The stimulus that promotes ovulation of the ovarian follicle also leads to the conversion of the follicle into the corpus luteum. The corpus luteum is the structure in the ovary which produces progesterone to maintain pregnancy. Progesterone is also a major ingredient in birth control pills. By preventing the stimulus that promotes ovulation and corpus luteum formation, both fertilization and pregnancy are prevented.

The stimulus that promotes both ovulation of the ovarian follicle and formation of the corpus luteum is the mid-cycle surge of luteinizing hormone (LH) from the pituitary gland. LH levels in the blood remain significantly elevated in humans for approximately 24 hours. With the initial rise in blood LH levels, LH binds to receptors on the surface of ovarian granulosa and thecal cells, resulting in the activation of the receptor. The active LH receptor then initiates a signal which is propagated via a signal transduction pathway to the nucleus. The signal reaches the nucleus within one minute of LH receptor activation. Once the signal reaches the nucleus, specific genes are turned on while others are turned off, resulting in events which lead in ovulation and corpus luteum formation. [See model on opposite page]

Despite the continued presence of relatively high concentrations of LH in the blood, the active LH receptor rapidly becomes inactivated or desensitized. The desensitized LH receptor looses its ability to signal some pathways, but gains the ability to signal other pathways. It is hypothesized that the loss of signaling activity down some pathways is obligatory for oocyte maturation to allow for fertilization, as well as events associated with ovulation and luteinization. It is also hypothesized that the "other" pathways now activated by the "desensitized" LH receptor or in response to LH receptor desensitization participate in ovulation and corpus luteum formation.

Recent studies in the laboratory of Mary Hunzicker-Dunn of the Department of Cellular and Molecular Biology by Dr. Sutapa Mukherjee, a Lalor Foundation Fellow, have elucidated part of the mechanism by which the LH receptor becomes desensitized. This novel mechanism for LH receptor desensitization involves the protein beta-arrestin, which binds to the active LH receptor and "arrests" its signaling down a specific pathway. These investigators found that beta-arrestin is "docked" in the plasma or outer membrane of ovarian granulosa cells, the same place where the LH receptors are located. The novel aspect of this mechanism is that the LH receptor activates a small signaling cascade of its own in the plasma membrane, resulting in the release of beta-arrestin from its membrane docking site and binding of beta-arrestin to the LH receptor. This laboratory has identified a key player in this pathway, a protein named ARF6, or ADP ribosylation factor 6. Activation of ARF6 in response to LH receptor activation results in the release of beta-arrestin from its docking site. The release of beta-arrestin from its membrane docking site can be prevented by inhibiting the activation of ARF6. Similarly, the release of beta-arrestin from its membrane docking site can be stimulated in the absence of LH receptor activation by an activator of ARF6.

The LH receptor is believed to have a looped structure that criss-crosses the plasma membrane of cells seven times, resulting in loops outside of the cell (or extracellular loops) and loops inside the cell or intracellular loops. The hormone LH binds to the extracellular loops of the receptor. The Hunzicker-Dunn laboratory has shown that upon release of beta-arrestin from its membrane docking site, beta-arrestin binds very tightly to the third intracellular loop of the LH receptor. This binding to the LH receptor prevents the receptor from signaling to the protein that promotes increased production of the second messenger, cAMP. This laboratory has also shown that a synthetic peptide corresponding to the beta-arrestin binding sites on the LH receptor completely prevents LH receptor desensitization. These investigators are initiating studies to determine in the intact cell, and ultimately in the intact animal, what the physiological consequence of blocking LH receptor desensitization will be on events such as ovulation, luteinization and corpus luteum formation, and oocyte maturation.

LH receptor desensitization might also contribute to precocious puberty in males, or testotoxicosis. Dr. Andrew Shenker, of the Department of Pediatrics, reported in 1993 that testotoxicosis results from the presence of a constitutively active LH receptor in the testis resulting from a mutation in the amino acid sequence of this protein. This is a receptor that does not require LH binding to promote activation. It is also possible that the constitutive activity of this receptor results not only from the formation of an active conformation of the receptor as a result of the identified mutations but also because the receptor cannot become desensitized. Future studies by the Hunzicker-Dunn laboratory in collaboration with Dr. Shenker will seek to determine whether beta-arrestin can bind to the constitutively active LH receptor. If beta-arrestin cannot bind to the constitutively receptor, this result would suggest that the inibility of this receptor to bind beta-arrestin and become desensitized likely contributes to its constitutive activity. By understanding the biochemical bases for the constitutively active LH receptor, clinical solutions to regulate the activity of this receptor can be approached.

Receptor desensitization occurs not only for the LH receptor but also for the some 1000 other seven membrane-spanning receptors in this family of proteins. These receptors regulate/determine many critical functions in the body, including adrenal function, thyroid function, growth, cardiac function, and the sense of taste . It is not known whether the novel events which mediate desensitization of the LH receptor are unique to this single receptor or whether these events apply to one or more of the other many receptors in this large family of proteins. Future studies are required to answer these important biological questions.

References:

Mukherjee S, Palczewski K, Gurevich V, Benovic JL, Banga P, Hunzicker-Dunn M. (1999) A direct role for arrestins in desensitization of the Luteinizing Hormone/choriogonadotropin-receptor in porcine ovarian follicular membranes. Proc Natl Acad Sci 96, 493-498.

Mukherjee S, Palczewski K, Gurevich VV, Hunzicker-Dunn M. (1999) ß arrestin-dependent desensitization of luteinizing hormone/choriogonadotropin receptor is prevented by a synthetic peptide to the third intracellular loop of the receptor. J Biol. Chem, 274, 12984-12989.

Mukherjee S, Casanova JE, Hunzicker-Dunn M. (2001) Desensitization of the luteinizing hormone/choriogonadotropin receptor in ovarian follicular membranes is inhibited by catalytically inactive ARNO. J Biol Chem 276, 6524-6528.

Achermann, J.C., Ito M. and Jameson, J.L. (2000) A naturally-occurring steroidogenic factor-1 (SF-1) mutation exhibits differential binding and activation of target genes. J Biol Chem 275:31708-31714.

Bengtson, N.W. and Linzer, D.I.H. (2000) Inhibition of tumor growth by the antiangiogenic placental hormone, proliferin-related protein. Mol Endocricol 14:1934-1943.

Chatterton, R.T. Jr., Hill, P.D., Aldah, J.C., Hodges, K.R., Belknap, S.M. and Zinaman, M.J. (2000) Relation of plasma oxytocin and prolactin concentrations to milk production in mothers of preterm infants: influence of stress. J Clin Endocrinol Metab 85:3661-3668.

Horton, T.H. and Yellon, S.M. Aging, reproduction, and the melatonin rhythm in the Siberian hamster. J Biol Rhythms (in press).

Klein, N.A., Battaglia D.E., Woodruff T.K., Padmanabhan, V., Giudice, L.C., Bremmer, W.J. and Soules, M.R. (2000) Ovarian follicular concentrations of activin, follistatin, inhibin, insulin-like growth factor I (IGF-I), IGF-II, IGF-binding protein-2 (IGFBP-2), and vascular endothelial growth factor in spontaneous menstrual cycles of normal women of advanced reproductive age. J Clin Endocrinol Metab 85:4520-4525.

Low-Zeddies, S.S. and Takahashi, J.S. (2001). Chimera analysis of the Clock mutation in mice shows that complex celluar integration determines circadian behavior. Cell 105:25-42.

MacGregor, S.J., Liu H., Bentrem, D.J., Zapf, J.W. and Jordan, V.C. (2000) Allosteric silencing of activating function 1 in the 4-hydroxytamoxifen estrogen receptor complex is induced by substituting glycine for aspartate at amino acid 351. Cancer Res 60:5097-105.

Mayo, K.E., Miller, T., DeAlmeida, V., Godfrey, P., Zheng, J. and Cunha, S. (2000) Regulation of the pituitary somatotroph cell by GNRH and its receptor. Recent Progress in Hormone Research (ed. P.M. Conn), 55:237-267.

McDade, T.W., Beck, M.A., Kuzawa, C. and Adair, L.S. Prenatal undernutrition and postnatal growth are associated with adolescent thymic function. Journal of Nutrition (in press).

Tufts, R and Wang, Z. Androgen regulation of the largest subunit of RNA polymerase II in the rat ventral prostate. Journal of Steroid Biochemistry & Molecular Biology, November 2000 (in press).

Turek, F.W. (2000) From the simple to the complex and back again: dissecting the mammalian circadian clock system and implications for sleep research. In: Zeitgebers, Entrainment and masking of the circadian system. Honma, K and Hornma, S. (eds), Hokkaido University Press, Sapporo, pp. 227-238.

Yankova, M., Hart, S.A. and Woolley, C.S. (2001) Estrogen increases synaptic connectivity between single presynaptic boutons and multiple postsynaptic CA1 pyramidal cells: a serial electron microscopic study. PNAS 98(6), pp. 3525-3530.

Yudin, A.I., Goldberg, E., Robertson, K.R. and Overstreet, J.W. (2000) Calpain and calpastatin are located between the plasma membrane and outer acrosomal membrane of cynomologus macaque spermatoza. J Androl 21:721-729.