PDF(Pubmed)
Abstract：
MAPK activating death domain (MADD) is a multifunctional protein regulating small GTPases RAB3 and RAB27, MAPK signaling, and cell survival. Polymorphisms in the MADD locus are associated with glycemic traits, but patients with biallelic variants in MADD manifest a complex syndrome affecting nervous, endocrine, exocrine, and hematological systems. We identified a homozygous splice site variant in MADD in 2 siblings with developmental delay, diabetes, congenital hypogonadotropic hypogonadism, and growth hormone deficiency. This variant led to skipping of exon 30 and in-frame deletion of 36 amino acids. To elucidate how this mutation causes pleiotropic endocrine phenotypes, we generated relevant cellular models with deletion of MADD exon 30 (dex30). We observed reduced numbers of β cells, decreased insulin content, and increased proinsulin-to-insulin ratio in dex30 human embryonic stem cell-derived pancreatic islets. Concordantly, dex30 led to decreased insulin expression in human β cell line EndoC-βH1. Furthermore, dex30 resulted in decreased luteinizing hormone expression in mouse pituitary gonadotrope cell line LβT2 but did not affect ontogeny of stem cell-derived GnRH neurons. Protein-protein interactions of wild-type and dex30 MADD revealed changes affecting multiple signaling pathways, while the GDP/GTP exchange activity of dex30 MADD remained intact. Our results suggest MADD-specific processes regulate hormone expression in pancreatic β cells and pituitary gonadotropes.
摘要：
MAPK激活死亡域(MADD)是调节小GTPasesRAB3和RAB27、MAPK信号传导的多功能蛋白,细胞存活。MADD位点的多态性与血糖性状相关，但是MADD双等位基因变异的患者表现出一种影响神经的复杂综合征，内分泌，外分泌，和血液系统。我们在2个发育迟缓的兄弟姐妹中鉴定了MADD中的纯合剪接位点变异，糖尿病,先天性低促性腺激素性性腺功能减退，生长激素缺乏症.该变体导致外显子30的跳跃和36个氨基酸的框内缺失。为了阐明这种突变是如何引起多效性内分泌表型的，我们建立了MADD外显子30缺失的相关细胞模型(dex30).我们观察到β细胞数量减少，胰岛素含量降低，并增加了dex30人胚胎干细胞来源的胰岛中胰岛素原与胰岛素的比率。和谐地，dex30导致人β细胞系EndoC-βH1中胰岛素表达降低。此外，dex30导致小鼠垂体促性腺激素细胞系LβT2中黄体生成素的表达降低，但不影响干细胞来源的GnRH神经元的个体发育。野生型和dex30MADD的蛋白质-蛋白质相互作用揭示了影响多个信号通路的变化，而dex30MADD的GDP/GTP交换活动保持完整。我们的结果表明，MADD特异性过程调节胰腺β细胞和垂体促性腺激素的激素表达。
