Membrane organization of luteinizing hormone receptors during signal transduction
Date
2010
Authors
Wolf-Ringwall, Amber L., author
Roess, Deborah, advisor
Miller, Charles, committee member
Graham, James, committee member
Barisas, B. George, committee member
Journal Title
Journal ISSN
Volume Title
Abstract
Mechanisms involved in signal transduction by luteinizing hormone (LH) receptors are important for regulating key events in mammalian reproduction, such as ovulation, sex hormone production and maintenance of pregnancy. Studying the organization of LH receptors in the plasma membrane during hormone-mediated signaling provides insights into the protein interactions needed for important physiological responses. We used biochemical and biophysical methods to examine the role of the plasma membrane in contributing to LH receptor desensitization. Using single particle tracking and sucrose gradient ultracentrifugation, we determined that individual human LH receptors are confined in small membrane compartments and localize in membrane rafts for several hours following desensitization. These receptors do not demonstrate signaling via cyclic adenosine monophosphate (cAMP) while they are confined, suggesting that the microenvironment within these compartments may be different for desensitized versus actively signaling receptors. We also investigated self-association of human LH receptors using homotransfer fluorescence resonance energy transfer (homo-FRET) and fluorescence correlation spectroscopy. We determined that human LH receptors self-associate following desensitization and in response to increasing concentrations of human chorionic gonadotropin (hCG). LH receptors demonstrated the highest degree of aggregation in response to saturating concentrations of 100 nM hCG. Using single particle tracking, we examined whether native LH receptors expressed on KGN human granulosa-like tumor cells, or M l7 human neuroblastoma cells, become confined in small membrane compartments in response to hormone binding. We found that confinement of native LH receptors in small plasma membrane compartments depended on hCG concentration. With increasing concentrations of hCG, more LH receptors became confined in small membrane compartments with an average diameter of less than 100 nm. These receptors also exhibited slower rates of lateral diffusion. We reported the movement of non-functional hormone-receptors, labeled with deglycosylated hCG, into small membrane compartments in response to hCG treatment that saturated other available LH receptors on the membrane. This finding suggests that interactions between functional and non-functional LH receptors may occur in membrane microdomains during signal transduction.
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Covers not scanned.
Print version deaccessioned 2022.
Print version deaccessioned 2022.
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Subject
Luteinizing hormone -- Receptors
Chorionic gonadotropins