Familial, apparently autosomal dominant, early-onset forms of diabetes mellitus of the adulthood that are negative for mutations in known MODY genes have been repeatedly described. Except that for their age of onset, these forms of diabetes resemble classical type 2 diabetes (T2D), thereby suggesting that they are due to mutations in genes modulating insulin sensitivity and for the fine tuning of insulin secretion rather than in genes playing a central role in insulin synthesis/secretion, as is the case for MODY. To identify genetic causes of these forms of diabetes, whole exam sequencing was carried out in portends from 59 families from Italy and the U.S. Two mutations in the APPL1 gene (a L552X stop-codon and a D94N missense mutation), showing segregation with diabetes, were found in two different families. Neither mutation had been previously reported in publicly available databases. APPL1 binds to Akt2 and positively modulates insulin-mediated Akt2 activation and downstream signaling, which is involved in both insulin action and secretion. Accordingly, APPL1 ablation causes insulin resistance and impaired glucose homeostasis in mice. X552, N94 and wild type (WT) APPL1 cDNAs were transfected in HepG2 cells, followed by evaluation of mRNA and protein expression levels along with insulin-stimulated Akt2-ser473 and GSK3β-ser9 phosphorylation. X552 totally abolished APPL1 protein (but not mRNA) expression, consistent with its being a stop-codon mutation. N94 APPL1 was expressed at the same level as WT APPL1; however, it caused significant reduction in the enhancement of insulin-stimulated Akt2 and GSK3β phosphorylation observed after WT APPL1 transfection as compared to un-transfected cells, therefore behaving as a loss of function mutation. Both mutations were absent in 2970 T2D patients and in 1639 control subjects. This is the first evidence of APPL1 mutations contributing to familial forms of diabetes mellitus of the adulthood and reaffirms the critical role of this gene in glucose homeostasis.
Mutations in APPL1 gene may contribute to familial diabetes mellitus / S., Prudente; P., Jungtrakoon; A., Marucci; O., Ludovico; T., Mazza; T., Hastings; E., Morini; L., Mercuri; Bailetti, Diego; C., Mendonca; F., Alberico; Basile, Giorgio; M., Romani; E., Miccinilli; M., Carella; F., Barbetti; Trischitta, Vincenzo; R., Di Paola; A., Doria. - In: DIABETES. - ISSN 0012-1797. - (2014). (Intervento presentato al convegno American Diabetes Association (ADA) 74th Annual Scientific Sessions tenutosi a San Francisco nel Giugno 2014) [10.2337/db14-1-388].
Mutations in APPL1 gene may contribute to familial diabetes mellitus
S. Prudente;BAILETTI, DIEGO;BASILE, GIORGIO;TRISCHITTA, VINCENZO;
2014
Abstract
Familial, apparently autosomal dominant, early-onset forms of diabetes mellitus of the adulthood that are negative for mutations in known MODY genes have been repeatedly described. Except that for their age of onset, these forms of diabetes resemble classical type 2 diabetes (T2D), thereby suggesting that they are due to mutations in genes modulating insulin sensitivity and for the fine tuning of insulin secretion rather than in genes playing a central role in insulin synthesis/secretion, as is the case for MODY. To identify genetic causes of these forms of diabetes, whole exam sequencing was carried out in portends from 59 families from Italy and the U.S. Two mutations in the APPL1 gene (a L552X stop-codon and a D94N missense mutation), showing segregation with diabetes, were found in two different families. Neither mutation had been previously reported in publicly available databases. APPL1 binds to Akt2 and positively modulates insulin-mediated Akt2 activation and downstream signaling, which is involved in both insulin action and secretion. Accordingly, APPL1 ablation causes insulin resistance and impaired glucose homeostasis in mice. X552, N94 and wild type (WT) APPL1 cDNAs were transfected in HepG2 cells, followed by evaluation of mRNA and protein expression levels along with insulin-stimulated Akt2-ser473 and GSK3β-ser9 phosphorylation. X552 totally abolished APPL1 protein (but not mRNA) expression, consistent with its being a stop-codon mutation. N94 APPL1 was expressed at the same level as WT APPL1; however, it caused significant reduction in the enhancement of insulin-stimulated Akt2 and GSK3β phosphorylation observed after WT APPL1 transfection as compared to un-transfected cells, therefore behaving as a loss of function mutation. Both mutations were absent in 2970 T2D patients and in 1639 control subjects. This is the first evidence of APPL1 mutations contributing to familial forms of diabetes mellitus of the adulthood and reaffirms the critical role of this gene in glucose homeostasis.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
