Intracellular trafficking effects of Insulin-Like Growth Factor Acid Labile Subunit gene (IGFALS) mutations identified in idiopathic short stature (ISS) children.

GUIDA C; NITCHKE R; DOMENÉ H; KARABATAS L; SCAGLIA P; MARTÍNEZ A; KESELMAN A; CASSINELLI H; BERGADÁ I; BENGOLEA S; PIPMAN V; HEINRICH J; ROPELATO G; BALLERINI G; REY R; JASPER H

Congreso; The XXI Annual Meeting of the Latin American Society for Pediatric Endocrinology (SLEP); 2010

Heterozygous IGFALS gene mutations are present in 11.2% of ISS children. Three of these mutations (P287L, A330D and R548W) were selected to determine their in vitro effects on intracellular ALS trafficking. ALS, IGFBP-3 and IGF-I serum levels were <-2 SDS in the patients carrying the P287L or R548W mutations but normal in the patient with A330D. The effects of the mutations on intracellular trafficking were studied by generating expression vectors of ALS, wild type (WT) or mutated, tagged to a fluorescent protein (pECFP-N1-ALS). CHO cells were cotransfected with pECFP-N1-ALS WT or mutated and a fluorescent trans-Golgi marker vector, TGN38.YFP. We found a significant increase in localization of P287L and R548W ALS mutants, but not of A330D, in trans-Golgi as compared to ALS-WT (Pearson’s colocalization coefficient between ALS and TGN38, mean±SE: WT 0.32±0.03; P287L 0.46±0.03; A330D 0.27±0.02; R548W 0.48±0.03; ANOVA p<0.0008, Tukey: P287L vs WT p<0.05; A330D vs WT p>0.05; R548W vs WT p<0.05). Our findings indicate that P287L and R548W ALS mutants affect the intracellular trafficking of ALS and could be involved in the short stature phenotype of both patients since they are associated to low serum levels of ALS, IGFBP3 and IGF-I.