ABSTRACT
Rab5 is a master regulator for endosome biogenesis and transport while its in vivo physiological function remains elusive. Here, we find that Rab5a is upregulated in several in vivo and in vitro myogenesis models. By generating myogenic Rab5a-deficient mice, we uncover the essential roles of Rab5a in regulating skeletal muscle regeneration. We further reveal that Rab5a promotes myoblast differentiation and directly interacts with insulin receptor substrate 1 (IRS1), an essential scaffold protein for propagating IGF signaling. Rab5a interacts with IRS1 in a GTP-dependent manner and this interaction is enhanced upon IGF-1 activation and myogenic differentiation. We subsequently identify that the arginine 207 and 222 of IRS1 and tyrosine 82, 89, and 90 of Rab5a are the critical amino acid residues for mediating the association. Mechanistically, Rab5a modulates IRS1 activation by coordinating the association between IRS1 and the IGF receptor (IGFR) and regulating the intracellular membrane targeting of IRS1. Both myogenesis-induced and IGF-evoked AKT-mTOR signaling are dependent on Rab5a. Myogenic deletion of Rab5a also reduces the activation of AKT-mTOR signaling during skeletal muscle regeneration. Taken together, our study uncovers the physiological function of Rab5a in regulating muscle regeneration and delineates the novel role of Rab5a as a critical switch controlling AKT-mTOR signaling by activating IRS1.
Subject(s)
Cell Differentiation , Insulin Receptor Substrate Proteins/metabolism , Insulin-Like Growth Factor I/metabolism , Muscle, Skeletal/physiology , Myoblasts/cytology , Proto-Oncogene Proteins c-akt/metabolism , Regeneration/physiology , rab5 GTP-Binding Proteins/metabolism , Animals , Cell Line , HEK293 Cells , Hindlimb/metabolism , Humans , Intracellular Membranes/metabolism , Mice, Inbred C57BL , Muscle Development/genetics , Myoblasts/metabolism , Protein Binding , RNA, Small Interfering/metabolism , Receptor, IGF Type 1/metabolism , Signal Transduction , TOR Serine-Threonine Kinases/metabolism , Up-Regulation/genetics , rab5 GTP-Binding Proteins/geneticsABSTRACT
Oligodendrocytes (OLs) myelinate axons and provide electrical insulation and trophic support for neurons in the central nervous system (CNS). Platelet-derived growth factor (PDGF) is critical for steady-state number and differentiation of oligodendrocyte precursor cells (OPCs), but its downstream targets are unclear. Here, we show for the first time that Gab1, an adaptor protein of receptor tyrosine kinase, is specifically expressed in OL lineage cells and is an essential effector of PDGF signaling in OPCs in mice. Gab1 is downregulated by PDGF stimulation and upregulated during OPC differentiation. Conditional deletions of Gab1 in OLs cause CNS hypomyelination by affecting OPC differentiation. Moreover, Gab1 binds to downstream GSK3ß and regulated its activity, and thereby affects the nuclear accumulation of ß-catenin and the expression of a number of transcription factors critical to myelination. Our work uncovers a novel downstream target of PDGF signaling, which is essential to OPC differentiation and CNS myelination.
Subject(s)
Adaptor Proteins, Signal Transducing/metabolism , Cell Differentiation/physiology , Central Nervous System/metabolism , Oligodendrocyte Precursor Cells/metabolism , Oligodendroglia/metabolism , Platelet-Derived Growth Factor/metabolism , Adaptor Proteins, Signal Transducing/genetics , Animals , Catenins , Cell Lineage , Central Nervous System/cytology , Gene Expression Regulation , Mice , Mice, Knockout , Protein-Tyrosine Kinases/metabolism , RNA, Small Interfering , Receptors, Growth Factor/metabolism , Signal Transduction , Transcription Factors , TranscriptomeABSTRACT
Since the publication of the article, the authors became aware that Figs. 1c, 5k and 6m contained errors in representative image and PAS score in control groups. The corrected Figs. 1c, 5k, and 6m are given below, and the figure legends are the same as original.
ABSTRACT
Shp2 is a non-receptor protein tyrosine phosphatase containing two Src homology 2 (SH2) domains that is implicated in intracellular signaling events controlling cell proliferation, differentiation and migration. To examine the role of Shp2 in brain development, we created mice with Shp2 selectively deleted in neural stem/progenitor cells. Homozygous mutant mice exhibited early postnatal lethality with defects in neural stem cell self-renewal and neuronal/glial cell fate specification. Here we report a critical role of Shp2 in guiding neuronal cell migration in the cerebellum. In homozygous mutants, we observed reduced and less foliated cerebellum, ectopic presence of external granule cells and mispositioned Purkinje cells, a phenotype very similar to that of mutant mice lacking either SDF-1alpha or CXCR4. Consistently, Shp2-deficient granule cells failed to migrate toward SDF-1alpha in an in vitro cell migration assay, and SDF-1alpha treatment triggered a robust induction of tyrosyl phosphorylation on Shp2. Together, these results suggest that although Shp2 is involved in multiple signaling events during brain development, a prominent role of the phosphatase is to mediate SDF-1alpha/CXCR4 signal in guiding cerebellar granule cell migration.
Subject(s)
Cell Movement/physiology , Cerebellum/growth & development , Chemokine CXCL12/metabolism , Protein Tyrosine Phosphatase, Non-Receptor Type 11/metabolism , Receptors, CXCR4/metabolism , Animals , Brain/metabolism , Cell Differentiation , Chemokine CXCL12/genetics , Mice , Mice, Transgenic , Phosphorylation , Protein Tyrosine Phosphatase, Non-Receptor Type 11/genetics , Receptors, CXCR4/genetics , Signal Transduction/physiologySubject(s)
Chromosomes, Human, Y , DNA, Mitochondrial/genetics , Haplotypes , Polymorphism, Genetic , China/ethnology , Gene Frequency , HumansABSTRACT
The frequency of Y-chromosome haplotypes consisted of thirteen single nucleotide polymorphism alleles in Bouyei people was investigated using PCR-RFLP. And the polymorphism of mitochondrial DNA Region V was studied. Nine Y-chromosome haplotypes (H1, H4, H5, H6, H7, H8, H9, H11, H12) and two mtDNA alleles (9-bp deletion) were obtained in the samples. The frequency distribution of these haplotypes and mtDNA polymorphisms in Bouyei people were very similar to that in Daic speaking populations including Zhuang, Li, Dong, and Yao people from Jinxiu, indicating a close genetic relationship among those populations implicating a common ancestry. A hypothesis of the origin of Bouyei people was proposed.
