Colin M. Clay, PhD
Professor and Head
Office: W137 ARBL Building, Foothills Campus
I coordinate and teach in the second semester of the graduate course in Mammalian Physiology. I also teach sections of Metabolic Endocrinology, Mechanisms of Hormone Action and Animal Biotechnoloy. Finally, I teach an undergraduate course entitled Drugs and the Human Body.
Research Interests -- Molecular Regulation of the GnRH Receptor
The interaction of the hypothalamic peptide termed gonadotropin releasing hormone (GnRH) with specific receptors located on gonadotrope cells of the anterior pituitary gland represents a central point for regulation of reproductive function. One of our primary research goals is to define the molecular mechanisms underlying transcriptional regulation of the GnRHR gene. We have cloned the gene encoding the GnRHR and have found that cell-specific expression of this gene is mediated by a complex enhancer whose components include a binding site for the nuclear orphan receptor steroidogenic factor-1 (SF-1), a canonical AP-1 element, and an element we have termed the GnRH receptor activating sequence or GRAS. In addition to mediating cell-specific expression, this complex enhancer also integrates multiple endocrine inputs. First, AP-1 appears to be the operative element that mediates GnRH responsiveness of the GnRHR gene via MAPkinase mediated recruitment of Jun and Fos family members. Second, we have discovered that GRAS functionally co-localizes with activin regulation of the GnRHR gene promoter. Our most recent data suggests that GRAS represents a composite regulatory element whose functional activity is partially dependent on a distal binding site for members of the SMAD family of TGFb/activin signaling proteins. Much of our work depends on analyses of promoter function in permanent cell lines; however, when possible, we seek to expand our studies to a more physiological setting such as transgenic mice.
Our goals are to understand the GnRHR at both the genetic and protein level. Toward the latter, we have constructed functional GnRH receptors in which green fluorescent protein (GFP) and spectral variants of GFP are fused to the intracellular carboxyl terminus. These intrinsically fluorescent molecules have afforded us an opportunity to study the GnRH receptors as both an occupied and unoccupied receptor. For example, we have used fluorescence resonance energy transfer (FRET) to demonstrate that agonist but not antagonist induces self-association of GnRH receptors in the plasma membrane. We suggest that this self-association is a critical event preceding signal transduction by the G-protein coupled GnRHR. Based on more recent experiments we further suggest that agonist "driven" GnRHR self-association occurs in the context of discrete plasma membrane microdomains referred to as lipid rafts.
For additional information on current projects, consult the page on Hypothalamic and Pituitary Function.
Duval DL, Ellsworth BS, Clay CM. 1999. Is gonadotrope expression of the gonadotropin releasing hormone receptor gene mediated by autocrine/paracrine stimulation of an activin response element? Endocrinology 140:1949-1952.
Horvat RD, Roess DA, Nelson SE, Barisas BG, Clay CM. 2001. Binding of agonist but not antagonist leads to fluorescence resonance energy transfer between intrinsically fluorescent GnRH receptors. Mol Endocrinol 15:695-703.
Ellsworth BS, White BR, Burns AT, Cherrington BD, Otis AM, Clay CM. 2003. c-Jun-N-terminal nase (JNK) activation of AP-1 underlies homologous regulation of the gonadotropin-releasing hormone receptor gene. Endocrinology 144:839-849.
Ellsworth BS, Escudero KW, Duval DL, Nelson SE, Clay CM. 2003. The gonadotropin releasing hormone (GnRH) receptor activating sequence (GRAS) is a composite regulatory element that interacts with multiple classes of transcription factors including Smads, AP-1 and a forkhead DNA binding protein. Mol Cell Endocrinol 206:93-111.
Navratil AM, Bliss SP, Berghorn KA, Haughian JM, Farmerie TA, Graham JK, Clay CM, Roberson MS. 2003. Constitutive localization of the gonadotropin-releasing hormone (GnRH) receptor to low-density membrane microdomains is necessary for GnRH signaling to ERK. J Biol Chem 278:131593-131602.