title: Appl1 is dispensable for mouse development, and loss of Appl1 has growth factor-selective effects on Akt signaling in murine embryonic fibroblasts.
abstract: The adaptor protein APPL1 (adaptor protein containing pleckstrin homology (PH), phosphotyrosine binding (PTB), and leucine zipper motifs) was first identified as a binding protein of AKT2 by yeast two-hybrid screening. APPL1 was subsequently found to bind to several membrane-bound receptors and was implicated in their signal transduction through AKT and/or MAPK pathways. To determine the unambiguous role of Appl1 in vivo, we generated Appl1 knock-out mice. Here we report that Appl1 knock-out mice are viable and fertile. Appl1-null mice were born at expected Mendelian ratios, without obvious phenotypic abnormalities. Moreover, Akt activity in various fetal tissues was unchanged compared with that observed in wild-type littermates. Studies of isolated Appl1(-/-) murine embryonic fibroblasts (MEFs) showed that Akt activation by epidermal growth factor, insulin, or fetal bovine serum was similar to that observed in wild-type MEFs, although Akt activation by HGF was diminished in Appl1(-/-) MEFs. To rule out a possible redundant role played by the related Appl2, we used small interfering RNA to knock down Appl2 expression in Appl1(-/-) MEFs. Unexpectedly, cell survival was unaffected under normal culture conditions, and activation of Akt was unaltered following epidermal growth factor stimulation, although Akt activity did decrease further after HGF stimulation. Furthermore, we found that Appl proteins are required for HGF-induced cell survival and migration via activation of Akt. Our studies suggest that Appl1 is dispensable for development and only participate in Akt signaling under certain conditions.
authors.affiliation: Cancer Genetics and Signaling Program, Fox Chase Cancer Center, Philadelphia, Pennsylvania 19111, USA.
authors.forename: Yinfei
authors.initials: Y
authors.lastname: Tan
authors.forename: Huihong
authors.initials: H
authors.lastname: You
authors.forename: Chao
authors.initials: C
authors.lastname: Wu
authors.forename: Deborah A
authors.initials: DA
authors.lastname: Altomare
authors.forename: Joseph R
authors.initials: JR
authors.lastname: Testa
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D000831:Animals, Newborn; D002352:Carrier Proteins / Q000235:genetics / Q000502:physiology*; D002465:Cell Movement; D002470:Cell Survival; D002478:Cells, Cultured; D047108:Embryonic Development / Q000187:drug effects; D005347:Fibroblasts / Q000378:metabolism*; D017228:Hepatocyte Growth Factor / Q000494:pharmacology*; D036341:Intercellular Signaling Peptides and Proteins / Q000494:pharmacology*; D051379:Mice; D018345:Mice, Knockout; D051057:Proto-Oncogene Proteins c-akt / Q000187:drug effects / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects
chemical_list: C464801:APPL1 protein, human; D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D036341:Intercellular Signaling Peptides and Proteins; D017228:Hepatocyte Growth Factor; D051057:Proto-Oncogene Proteins c-akt