The Inner Nuclear Membrane Protein Nemp1 Is a New Type of RanGTP-Binding Protein in Eukaryotes

摘要: The inner nuclear membrane (INM) protein Nemp1/TMEM194A has previously been suggested to be involved in eye development Xenopus, and contains two evolutionarily conserved sequences the transmembrane domains (TMs) C-terminal region, named region A B, respectively. To elucidate molecular nature of Nemp1, we analyzed its interacting proteins through those regions. First, found that Nemp1 interacts with itself lamin TMs A, Colocalization at INM suggests interaction participates localization Nemp1. Secondly, yeast two-hybrid screening using B as bait, identified small GTPase Ran a probable Nemp1-binding partner. GST pulldown co-immunoprecipitation assays mutants revealed binds directly GTP-bound effector domain. Immunostaining experiments transfected COS-7 cells full-length recruits near envelope, suggesting role for accumulation RanGTP periphery. At neurula-to-tailbud stages Xenopus embryos, nemp1 expression overlapped ran several regions including vesicles. Co-knockdown antisense morpholino oligos caused reduction cell densities severe defects more strongly than either single knockdown alone, their functional interaction. Finally show Arabidopsis thaliana Nemp1-orthologous interact A. Ran, evolutionally physical interactions possibly basic cellular functions transportation. Taken together, conclude represents new type RanGTP-binding protein.