RESUMO
Polypyrimidine tract binding protein 1 (PTBP1) is thought to be expressed only at embryonic stages in central neurons. Its down-regulation triggers neuronal differentiation in precursor and non-neuronal cells, an approach recently tested for generation of neurons de novo for amelioration of neurodegenerative disorders. Moreover, PTBP1 is replaced by its paralog PTBP2 in mature central neurons. Unexpectedly, we found that both proteins are coexpressed in adult sensory and motor neurons, with PTBP2 restricted mainly to the nucleus, while PTBP1 also shows axonal localization. Levels of axonal PTBP1 increased markedly after peripheral nerve injury, and it associates in axons with mRNAs involved in injury responses and nerve regeneration, including importin ß1 (KPNB1) and RHOA. Perturbation of PTBP1 affects local translation in axons, nociceptor neuron regeneration and both thermal and mechanical sensation. Thus, PTBP1 has functional roles in adult axons. Hence, caution is required before considering targeting of PTBP1 for therapeutic purposes.
Assuntos
Axônios , Regeneração Nervosa , Neurônios , Traumatismos dos Nervos Periféricos , Adulto , Humanos , Axônios/metabolismo , Ribonucleoproteínas Nucleares Heterogêneas/genética , Ribonucleoproteínas Nucleares Heterogêneas/metabolismo , Interneurônios/metabolismo , Regeneração Nervosa/genética , Neurônios/metabolismo , Traumatismos dos Nervos Periféricos/genética , Traumatismos dos Nervos Periféricos/metabolismoRESUMO
Size homeostasis is a fundamental process in biology and is particularly important for large cells such as neurons. We previously proposed a motor-dependent length-sensing mechanism wherein reductions in microtubule motor levels would be expected to accelerate neuronal growth, and validated this prediction in dynein heavy chain 1 Loa mutant (Dync1h1Loa) sensory neurons. Here, we describe a new mouse model with a conditional deletion allele of exons 24 and 25 in Dync1h1. Homozygous Islet1-Cre-mediated deletion of Dync1h1 (Isl1-Dync1h1-/-), which deletes protein from the motor and sensory neurons, is embryonic lethal, but heterozygous animals (Isl1-Dync1h1+/-) survive to adulthood with â¼50% dynein expression in targeted cells. Isl1-Dync1h1+/- sensory neurons reveal accelerated growth, as previously reported in Dync1h1Loa neurons. Moreover, Isl1-Dync1h1+/- mice show mild impairments in gait, proprioception and tactile sensation, similar to what is seen in Dync1h1Loa mice, confirming that specific aspects of the Loa phenotype are due to reduced dynein levels. Isl1-Dync1h1+/- mice also show delayed recovery from peripheral nerve injury, likely due to reduced injury signal delivery from axonal lesion sites. Thus, conditional deletion of Dync1h1 exons 24 and 25 enables targeted studies of the role of dynein in neuronal growth.
Assuntos
Dineínas do Citoplasma , Dineínas , Camundongos , Animais , Dineínas/genética , Dineínas/metabolismo , Dineínas do Citoplasma/genética , Dineínas do Citoplasma/metabolismo , Alelos , Mutação , Células Receptoras Sensoriais/metabolismoRESUMO
Nucleolin is a multifunctional RNA Binding Protein (RBP) with diverse subcellular localizations, including the nucleolus in all eukaryotic cells, the plasma membrane in tumor cells, and the axon in neurons. Here we show that the glycine arginine rich (GAR) domain of nucleolin drives subcellular localization via protein-protein interactions with a kinesin light chain. In addition, GAR sequences mediate plasma membrane interactions of nucleolin. Both these modalities are in addition to the already reported involvement of the GAR domain in liquid-liquid phase separation in the nucleolus. Nucleolin transport to axons requires the GAR domain, and heterozygous GAR deletion mice reveal reduced axonal localization of nucleolin cargo mRNAs and enhanced sensory neuron growth. Thus, the GAR domain governs axonal transport of a growth controlling RNA-RBP complex in neurons, and is a versatile localization determinant for different subcellular compartments. Localization determination by GAR domains may explain why GAR mutants in diverse RBPs are associated with neurodegenerative disease.
Assuntos
Nucléolo Celular/metabolismo , Gânglios Espinais/metabolismo , Cinesinas/metabolismo , Neurônios/metabolismo , Fosfoproteínas/química , Proteínas de Ligação a RNA/química , Nervo Isquiático/metabolismo , Sequência de Aminoácidos , Animais , Transporte Axonal/genética , Linhagem Celular Tumoral , Nucléolo Celular/ultraestrutura , Gânglios Espinais/citologia , Expressão Gênica , Células HEK293 , Células HeLa , Humanos , Cinesinas/genética , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Mutação , Neurônios/citologia , Fosfoproteínas/genética , Fosfoproteínas/metabolismo , Cultura Primária de Células , Domínios Proteicos , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Proteínas de Ligação a RNA/genética , Proteínas de Ligação a RNA/metabolismo , Nervo Isquiático/citologia , NucleolinaRESUMO
How is neuropathic pain regulated in peripheral sensory neurons? Importins are key regulators of nucleocytoplasmic transport. In this study, we found that importin α3 (also known as karyopherin subunit alpha 4) can control pain responsiveness in peripheral sensory neurons in mice. Importin α3 knockout or sensory neuron-specific knockdown in mice reduced responsiveness to diverse noxious stimuli and increased tolerance to neuropathic pain. Importin α3-bound c-Fos and importin α3-deficient neurons were impaired in c-Fos nuclear import. Knockdown or dominant-negative inhibition of c-Fos or c-Jun in sensory neurons reduced neuropathic pain. In silico screens identified drugs that mimic importin α3 deficiency. These drugs attenuated neuropathic pain and reduced c-Fos nuclear localization. Thus, perturbing c-Fos nuclear import by importin α3 in peripheral neurons can promote analgesia.
