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Instructor and Research Associate, University of Pittsburgh School of Medicine, Pittsburgh, PA 1998-2007
Postdoctoral: Endocrine Unit, Massachusetts General Hospital and Harvard Medical School, Boston, MA 1994-1998
Dartmouth Medical School, Hanover, NH, Ph.D. Pharmacology 1995
University of Toronto, Toronto, Canada, M.Sc. Pharmacology 1990
University of Toronto, Toronto, Canada, B.Sc. Chemical Physics 1985
Research Interests
The long-term goal of my research program is to understand the signaling of the Type I Parathyroid Hormone(PTH)/PTH-related peptide (PTHrP) receptor (PTH1R), and how it is regulated by cytoplasmic adaptor proteins such as the sodium/hydrogen exchanger regulatory factor 1 (NHERF1), also known as the ezrin binding protein of 50 kDa (EBP50). The biological action of PTH largely occurs in kidney and bone, where PTH1Rs are expressed in high numbers. The magnitude and duration of PTH action reflects the net balance between signal generation and signal termination by the PTH1R. We recently showed that the agonist, PTH(1-34), internalizes the PTH1R in renal proximal and distal tubule cells. Notably PTH(7-34), which binds to, but does not activate the PTH1R, internalizes the PTH1R only in distal tubule cells. Expression of NHERF1 in proximal and not distal tubule cells underlies the regulation of PTH(7-34)-induced PTH1R internalization Introduction of NHERF1 into distal tubule cells blocks PTH(7-34)-induced PTH1R internalization. Furthermore, we demonstrated that PTHrP(7-34) also internalizes the PTH1R in distal tubule cells but in a NHERF1-independent fashion. Using chimeric PTH/PTHrP peptides, we determined that F34 in PTH confers NHERF1-sensitivity to PTH1R internalization by N-terminally truncated PTH peptides. It is unclear how PTH(7-34) and PTHrP(7-34) affect the conformation of the PTH1R is such a way as to regulate NHERF1 effects on receptor internalization. Furthermore, little is known about what proteins interact with the full length PTH1R to determine the internalization response of the PTH1R to different peptide ligands. We presently have two lines of investigation that are addressing these issues.
First, usually advanced fluorescence microscopy techniques, we are measuring the trafficking of the PTH1R in response to PTH(7-34) and PTHrP(7-34) in the presence or absence of NHERF1 and ß-arrestins, another class of GPCR regulatory scaffolding proteins. We have determined using Image Cross Correlation Spectroscopy that PTHrP(7-34), like PTH(1-34), recruits ß-arrestin1 to the PTH1R. In contrast, PTH(7-34) does not recruit ß-arrestin1. Efforts in the lab are focusing on how PTH(7-34) internalizes the PTH1R in an arrestin-independent manner.
Second, we have identified, using split ubiquitin yeast two hybrid technology, a selenoprotein of 15 kDa (Sep15), that interacts with the PTH1R in its membrane-delimited context. Loss of heterozygosity (LOH) of Sep15 is associated with tumor progression in breast cancer. Increased dietary intake of selenium has also been shown to have a beneficial effect in preventing the incidence of cancer. LOH of NHERF1 is also associated with increased proliferation of breast tumor cell lines. The PTH-related protein (PTHrP) is also secreted by many breast tumors. We are currently investigating the role Sep15 and NHERF1 play in PTH1R trafficking and signaling in breast tumor epithelial cells and how it relates to their tumor suppressing mechanism of action.
:
1. Sneddon, W.B ., C. A. Syme, A. Bisello, C.E. Magyar, M. Driss Rochdi, J.L. Parent, E.J. Weinman, A.B. Abou-Samra and P.A. Friedman. 2003 Activation-independent parathyroid hormone receptor internalization is regulated by NHERF(EBP50). J. Biol. Chem. 278(44): 43787-43796
2. Sneddon W.B ., CE Magyar, GE Willick, CA Syme, F Galbiati, A Bisello, and PA Friedman. 2004. Ligand-selective dissociation of activation and internalization of the Parathyroid Hormone Receptor. Conditional efficacy of PTH peptide fragments. Endocrinology 145: 2815-2823.
3. Wheeler, D. and W.B. Sneddon. 2006. Mutation of Phenylalanine-34 of Parathyroid Hormone Disrupts NHERF1 Regulation of PTH Type I Receptor Signaling. Endocrine 30(3): 343-352
4. Sneddon, W.B., Y. Yang, J. Ba, L. Harinstein and PA Friedman. 2007. Extracellular Signal-Regulated Kinase Activation by Parathyroid Hormone in Distal Tubule Cells. Am. J. Physioll (Renal) 292(3):F1028-34.
5. Sneddon, W.B, and P.A. Friedman. 2007. ß-Arrestin-Dependent Parathyroid Hormone-Stimulated ERK Activation and PTH1R Internalization. Endocrinology 148(8):4073-9.
6. Wheeler, D., W.B. Sneddon , B. Wang, P.A. Friedman and G.G. Romero. 2007. Role of NHERF-1 and the Cytoskeleton in the Regulation of the Trafficking of G-Protein-Coupled Receptors. J. Biol. Chem. 2007 282(34):25076-87.
Contact Information
Office Phone: (412) 396-5615
Email: sneddonw@duq.edu |
