GERMLINE PROKR2 GENE VARIATIONS AFFECTING BOTH Gq- AND Gs-DEPENDENT INTRACELLULAR SIGNALS ARE FREQUENTLY ASSOCIATED WITH IDIOPATHIC CENTRAL HYPOGONADISM

Program: Abstracts - Orals, Featured Poster Presentations, and Posters
Session: SAT 134-163-GnRH & Gonadotroph Biology & Signaling
Bench to Bedside
Saturday, June 15, 2013: 1:45 PM-3:45 PM
Expo Halls ABC (Moscone Center)

Poster Board SAT-148
Marco Bonomi*1, Domenico Vladimiro Libri2, Gunnar Kleinau3, Marta Busnelli4, Fabiana Guizzardi1, Antonio Agostino Sinisi5, Angela Ida Pincelli6, Antonio Mancini7, Gianni Russo8, Paolo Beck-Peccoz9, Sandro Loche10, Mohamad Maghnie11, Csilla Krausz12 and Luca Persani13
1Istituto Auxologico Italiano IRCCS, Cusano Milanino, Italy, 2Istituto Auxologico Italiano IRCCS, Cusano Milanino, 20095, Italy, 3CharitÚ - Universitńtsmedizin Berlin, Berlin, Germany, 4Consiglio Nazionale delle Ricerche, Milano, Italy, 5Seconda UniversitÓ di Napoli, Napoli, Italy, 6Ospedale San Gerardo dei Tintori, Monza, Italy, 7Catholic University of the Sacred Heart, Rome, Italy, 8Ospedale San Raffaele, Milano, Italy, 9IRCCS CÓ Granda H Maggiore Policlinico, Milan, Italy, 10Ospedale Microcitemico, Cagliari, Italy, 11UniversitÓ di Genova, IRCCS Giannina Gaslini, Genova, Italy, 12UniversitÓ di Firenze, Florence, Italy, 13UniversitÓ di Milano, IRCCS Istituto Auxologico Italiano, Milan, Italy
Research on the prokineticin system over the past decade revealed several physiological functions in neurogenesis, regulation of circadian rhythms, metabolism, angiogenesis, pain perception, muscle contractility, hematopoiesis, immune response, thermoregulation and energy expenditure. The knockout mice models for both ligand and receptor revealed the role of PROK2 signaling in olfactory bulb (OB) morphogenesis and sexual maturation, suggesting PROK2 and PROKR2 as strong candidate genes for human GnRH deficiency. The involvement of the PROKR2/PROK2 pathway in the pathogenesis of the Idiopathic Central Hypogonadism (ICH) was first described in 2006 and subsequently reported in several other patients series. Here we present the results of the genetic screening in a series of 246 ICH patients where we found 4 novel (p.V158I, p.T260M, p.V334M, p.N15TfsX30) and 5 already known (p.L173R, p.R268C, p.V274D, p.V331M, p.H20MfsX23) germline variants in PROKR2 gene. We evaluated effects of these alterations on the two different PROKR2-mediated signaling pathways: IP3-Ca2+ (Gq-coupling) and cAMP (Gs-coupling). Expression levels in HEK293 cells were similar to the wild-type (wt) in the case of p.V158I, p.V331M, p.V334M and reduced by 50% for the other variants. Variants p.T260M, p.R268C and p.V331M showed no remarkable changes in cAMP EC50 while the IP3 signalling appeared strongly affected. In contrast, p.L173R and p.V274D presented no virtual response in terms of cAMP accumulation. Moreover, p.L173R had an IP3 response (EC50) similar to wt and p.V274D presented a 10-fold increase of IP3 EC50. Variant p.V334M lead to a 3-fold increase of EC50 for both cAMP and IP3. Based on advanced structural homology models, our findings provide structural insights on the transducing mechanisms of this interesting G protein-coupled receptor. In summary, the here described mutations at the PROKR2 are located at different spatial receptor regions and might cause modifications of receptor functions by diverse mechanisms. Moreover, the integrity of both PROKR2-dependent cAMP and IP3 signals is likely to be required for an adequate GnRH neuron function.

Nothing to Disclose: MB, DVL, GK, MB, FG, AAS, AIP, AM, GR, PB, SL, MM, CK, LP

*Please take note of The Endocrine Society's News Embargo Policy at http://www.endo-society.org/endo2013/media.cfm

Sources of Research Support: This work was supported by funds for Young Investigators from the Italian Ministry of Health (Grant No. GR2008-1137632) and IRCCS Istituto Auxologico Italiano (Ricerca Corrente Funds: 05C701).