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- 검색키워드
- 저자 : ( Kaushik Maiti ) (검색결과 4 건)
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Sujata Acharjee,Kaushik Maiti,Jae Mok Soh,Wook-Bin Im,Jae Young Seong,Hyuk Bang Kwon 한국분자세포생물학회 2002 Molecules and cells Vol.14 No.1
We previously demonstrated the presence of three dis-tinct types of the gonadotropin-releasing hormone re-ceptor (GnRHR) in a bullfrog (denoted bfGnRHR-1, bfGnRHR-2, and bfGnRHR-3). The bfGnRHRs exhib-ited differential tissue distribution and ligand selectiv-ity. In the present study, we demonstrated the desensi-tization and internalization kinetics of these receptors in both transiently-transfected HEK293 cells and ret-rovirus-mediated stable cells. The time-course accu-mulation of the inositol phosphate in response to GnRH revealed that bfGnRHR-1 and -2 were rapidly desensitized, whereas bfGnRHR-3 was slowly desensi-tized. A comparison of the internalization kinetics re-vealed the most rapid rate and highest extent of inter-nalization of bfGnRHR-2 among the three receptors. Interestingly, the mechanisms that underlie the recep-tor internalization appear to differ from each other. Internalization of bfGnRHR-1 was dependent on both dynamin and b-arrestin, whereas those of bfGnRHR-2 and -3 were dependent on dynamin, but not on b-arrestin. These results, therefore, suggest that differen-tial regulatory mechanisms for desensitization and internalization of the GnRHR are involved in diverse cellular and physiological responses to GnRH stimula-tion.
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Jae Young Seong,Kaushik Maiti,Jian Hua Li,Ai Fen Wang,Sujata Acharjee,Wang Phil Kim,임욱빈,권혁방 한국분자세포생물학회 2003 Molecules and cells Vol.16 No.2
ecently, we identified three types of non-mammalian gonadotropin-releasing hormone receptors (GnRHR) in the bullfrog (designated bfGnRHR-1-3), and a mammalian type-II GnRHR in green monkey cell lines (denoted gmGnRHR-2). All these receptors responded better to GnRH-II than GnRH-I, while mammalian type-I GnRHR showed greater sensitivity to GnRH-I than GnRH-II. In the present study, we designed new GnRH-II analogs and examined whether they acti- vated or inhibited non-mammalian and mammalian type-II GnRHRs. [D-Ala 6 ]GnRH-II, with D-Ala substi- tuted for Gly 6 in GnRH-II, increased inositol phos- phate (IP) production in cells stably expressing non- mammalian GnRHRs more effectively than native GnRH-II. However, it exhibited lower activity for mammalian type-I GnRHR than GnRH-I itself. Trptorelix-1, a GnRH-II antagonist, inhibited GnRH- induced IP production in cells expressing non- mammalian GnRHRs more effectively than Cetrorelix, a GnRH-I antagonist. Trptorelix-1, however, had lower potency for mammalian type-I GnRHR than Cetrorelix. Ligand-receptor binding assays revealed that [D-Ala 6 ]GnRH-II and Trptorelix-1 have higher affinities for non-mammalian GnRHRs but lower af- finities for mammalian type-I GnRHR than GnRH-II and Cetrorelix, respectively. Moreover, [D-Ala 6 ]GnRH- II and Trptorelix-1 had a higher affinity for gmGnRHR-2 than GnRH-II and Cetrorelix, respec- tively. These results indicate that [D-Ala 6 ]GnRH-II and Trptorelix-1 are highly effective agonist and antagonist, respectively, for non-mammalian and type- II mammalian GnRHRs
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Wang, Cheng bing,Oh, Da young,Maiti, Kaushik,Kwon, Hyuk bang,Cheon, Jun,Hwang, Jong iIk,Seong, Jae young Korean Society for Molecular Biology 2008 Molecules and cells Vol.25 No.1
The Glu/Asp<sup>7.32</sup> residue in extracellular loop 3 of the mammalian type-I gonadotropin-releasing hormone receptor (GnRHR) interacts with Arg<sup>8</sup> of GnRH-I, conferring preferential ligand selectivity for GnRH-I over GnRH-II. Previously, we demonstrated that the residues (Ser and Pro) flanking Glu/Asp<sup>7.32</sup> also play a role in the differential agonist selectivity of mammalian and non-mammalian GnRHRs. In this study, we examined the differential antagonist selectivity of wild type and mutant GnRHRs in which the Ser and Pro residues were changed. Cetrorelix, a GnRH-I antagonist, and Trptorelix-2, a GnRH-II antagonist, exhibited high selectivity for mammalian type-I and non-mammalian GnRHRs, respectively. The inhibitory activities of the antagonists were dependent on agonist concentration and subtype. Rat GnRHR in which the Ser-Glu-Pro (SEP) motif was changed to Pro-Glu-Val (PEV) or Pro-Glu-Ser (PES) had increased sensitivity to Trptorelix-2 but decreased sensitivity to Cetrorelix. Mutant bullfrog GnRHR-1 with the SEP motif had the reverse antagonist selectivity, with reduced sensitivity to Trptorelix-2 but increased sensitivity to Cetrorelix. These findings indicate that the residues flanking Glu<sup>7.32</sup> are important for antagonist as well as agonist selectivity.
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Li, Jian Hua,Choe, Han,Wang, Ai Fen,Maiti, Kaushik,Wang, Chengbing,Salam, Abdus,Chun, Sang Young,Lee, Won-Kyo,Kim, Kyungjin,Kwon, Hyuk Bang,Seong, Jae Young American Society for Pharmacology and Experimental 2005 Molecular pharmacology Vol.67 No.4
<P>Mammalian type I and II gonadotropin-releasing hormone (GnRH) receptors (GnRHRs) show differential ligand preference for GnRH-I and GnRH-II, respectively. Using a variety of chimeric receptors based on green monkey GnRHR-2 (gmGnRHR-2), a representative type II GnRHR, and rat GnRHR, a representative type I GnRHR, this study elucidated specific domains responsible for this ligand selectivity. A chimeric gmGnRHR-2 with the extracellular loop 3 (EL3) and EL3-proximal transmembrane helix 7 (TMH7) of rat GnRHR showed a great increase in ligand sensitivity to GnRH-I but not to GnRH-II. Point-mutation studies indicate that four amino acids, Leu/Phe(7.38), Leu/Phe(7.43), Ala/Pro(7.46), and Pro/Cys(7.47) in TMH7 are critical for ligand selectivity as well as receptor conformation. Furthermore, a combinatory mutation (Pro(7.31)-Pro(7.32)-Ser(7.33) motif to Ser-Glu-Pro in EL3 and Leu(7.38), Leu(7.43), Ala(7.46), and Pro(7.47) to those of rat GnRHR) in gmGnRH-2 exhibited an approximately 500-fold increased sensitivity to GnRH-I, indicating that these residues are critical for discriminating GnRH-II from GnRH-I. [Trp(7)]GnRH-I and [Trp(8)]GnRH-I but not [His(5)]GnRH-I exhibit a higher potency in activating wild-type gmGnRHR-2 than native GnRH-I, indicating that amino acids at positions 7 and 8 of GnRHs are more important than position 5 for differential recognition by type I and type II GnRHRs. As a whole, these data suggest a molecular coevolution of ligands and their receptors and facilitate the understanding of the molecular interaction between GnRHs and their cognate receptors.</P>
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