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Don · 15th April 2006, 11:44 AM

This article has absolutely nothing to do with either tanning or the science of UV. So why am I posting it? Because the "lead author" is my son Steve (who will get his PhD on May 12th) and his proud father just couldn't resist "bragging" about his son having a paper published in the prestigious scientific journal Endocrinology.

Luteinizing Hormone Receptors Translocate to Plasma Membrane Microdomains after Binding of Human Chorionic Gonadotropin

Steven M. L. Smith, Ying Lei, Jingjing Liu, Mary E. Cahill, Guy M. Hagen, B. George Barisas and Deborah A. Roess

Department of Biomedical Sciences (S.M.L.S., M.E.C., D.A.R.), Cell and Molecular Biology Program (Y.L., J.L.), and Department of Chemistry (G.M.H., B.G.B.), Colorado State University, Fort Collins, Colorado 80523

Receptor-mediated signal transduction by G protein-coupled receptors can involve redistribution of plasma membrane receptors into membrane structures that are characterized by insolubility in Triton X-100 and low buoyant density in sucrose gradients. Here we describe the translocation of wild-type (wt) rat LH receptors (LHR-wt) from the bulk membrane into membrane microdomains (rafts) after the binding of human chorionic gonadotropin (hCG). In sucrose gradient ultracentrifugation of plasma membranes from cells stably expressing FLAG-tagged LHR-wt, receptors were located in high-density membrane fractions before binding of hormone and in low-density fractions after hCG treatment. Receptor translocation to low-density sucrose fractions did not occur when cells were pretreated with 1% methyl-ß-cyclodextrin, which reduces membrane cholesterol and disrupts rafts. Single-particle tracking of individual FLAG-LHR-wt receptors showed that hCG-treated receptors become confined in small compartments with a diameter of 86 ± 36 nm, significantly smaller than 230 ± 79 nm diameter regions accessed by the untreated receptor. Receptors were no longer confined in these small compartments after disruption of rafts by methyl-ß-cyclodextrin, a treatment that also decreased levels of cAMP in response to hCG. Finally, translocation of LHR into rafts required a functional hormone-receptor complex but did not occur after extensive receptor cross-linking that elevated cAMP levels. Thus, retention of LHR in rafts or small membrane compartments is a characteristic of functional, hormone-occupied LHR-wt. Although raft translocation was not essential for cAMP production, it may be necessary for optimizing hormone-mediated signaling.

15th April 2006, 11:44 AM	#1 (permalink)
Don Veteran Join Date: Nov 2004 Location: USA Posts: 376	This article has nothing........ This article has absolutely nothing to do with either tanning or the science of UV. So why am I posting it? Because the "lead author" is my son Steve (who will get his PhD on May 12th) and his proud father just couldn't resist "bragging" about his son having a paper published in the prestigious scientific journal Endocrinology. Luteinizing Hormone Receptors Translocate to Plasma Membrane Microdomains after Binding of Human Chorionic Gonadotropin Steven M. L. Smith, Ying Lei, Jingjing Liu, Mary E. Cahill, Guy M. Hagen, B. George Barisas and Deborah A. Roess Department of Biomedical Sciences (S.M.L.S., M.E.C., D.A.R.), Cell and Molecular Biology Program (Y.L., J.L.), and Department of Chemistry (G.M.H., B.G.B.), Colorado State University, Fort Collins, Colorado 80523 Receptor-mediated signal transduction by G protein-coupled receptors can involve redistribution of plasma membrane receptors into membrane structures that are characterized by insolubility in Triton X-100 and low buoyant density in sucrose gradients. Here we describe the translocation of wild-type (wt) rat LH receptors (LHR-wt) from the bulk membrane into membrane microdomains (rafts) after the binding of human chorionic gonadotropin (hCG). In sucrose gradient ultracentrifugation of plasma membranes from cells stably expressing FLAG-tagged LHR-wt, receptors were located in high-density membrane fractions before binding of hormone and in low-density fractions after hCG treatment. Receptor translocation to low-density sucrose fractions did not occur when cells were pretreated with 1% methyl-ß-cyclodextrin, which reduces membrane cholesterol and disrupts rafts. Single-particle tracking of individual FLAG-LHR-wt receptors showed that hCG-treated receptors become confined in small compartments with a diameter of 86 ± 36 nm, significantly smaller than 230 ± 79 nm diameter regions accessed by the untreated receptor. Receptors were no longer confined in these small compartments after disruption of rafts by methyl-ß-cyclodextrin, a treatment that also decreased levels of cAMP in response to hCG. Finally, translocation of LHR into rafts required a functional hormone-receptor complex but did not occur after extensive receptor cross-linking that elevated cAMP levels. Thus, retention of LHR in rafts or small membrane compartments is a characteristic of functional, hormone-occupied LHR-wt. Although raft translocation was not essential for cAMP production, it may be necessary for optimizing hormone-mediated signaling.