RESUMEN
Inhibition of histone deacetylase 6 (HDAC6) was shown to support axon growth on the nonpermissive substrates myelin-associated glycoprotein (MAG) and chondroitin sulfate proteoglycans (CSPGs). Though HDAC6 deacetylates α-tubulin, we find that another HDAC6 substrate contributes to this axon growth failure. HDAC6 is known to impact transport of mitochondria, and we show that mitochondria accumulate in distal axons after HDAC6 inhibition. Miro and Milton proteins link mitochondria to motor proteins for axon transport. Exposing neurons to MAG and CSPGs decreases acetylation of Miro1 on Lysine 105 (K105) and decreases axonal mitochondrial transport. HDAC6 inhibition increases acetylated Miro1 in axons, and acetyl-mimetic Miro1 K105Q prevents CSPG-dependent decreases in mitochondrial transport and axon growth. MAG- and CSPG-dependent deacetylation of Miro1 requires RhoA/ROCK activation and downstream intracellular Ca2+ increase, and Miro1 K105Q prevents the decrease in axonal mitochondria seen with activated RhoA and elevated Ca2+ These data point to HDAC6-dependent deacetylation of Miro1 as a mediator of axon growth inhibition through decreased mitochondrial transport.
Asunto(s)
Histona Desacetilasa 6/genética , Mitocondrias/metabolismo , Neuronas/metabolismo , Proteínas de Unión al GTP rho/genética , Quinasas Asociadas a rho/genética , Acetilación/efectos de los fármacos , Animales , Transporte Axonal/efectos de los fármacos , Transporte Axonal/genética , Calcio/metabolismo , Proteoglicanos Tipo Condroitín Sulfato/farmacología , Femenino , Ganglios Espinales/citología , Ganglios Espinales/efectos de los fármacos , Ganglios Espinales/metabolismo , Regulación de la Expresión Génica , Histona Desacetilasa 6/metabolismo , Masculino , Ratones , Ratones Endogámicos C57BL , Mitocondrias/efectos de los fármacos , Glicoproteína Asociada a Mielina/farmacología , Neuronas/citología , Neuronas/efectos de los fármacos , Cultivo Primario de Células , Ratas , Ratas Sprague-Dawley , Transducción de Señal , Proteínas de Unión al GTP rho/metabolismo , Quinasas Asociadas a rho/metabolismoRESUMEN
CD4(+) T-cell lines (TCLs) from patients with clinically isolated syndromes (CIS) were selected with purified human myelin basic protein (MBP) and recombinant human myelin oligodendrocyte glycoprotein (rhMOG), at onset of neurological symptoms and when patients developed clinically definite multiple sclerosis (CDMS). The epitope specificity of each TCL was mapped with overlapping synthetic peptides. TCLs were assessed for their ability to secrete IFN-gamma, IL-4, and IL-6. Diverse patterns of epitope recognition were observed: (a) recognition of a broad spectrum of MBP peptide epitopes with evidence of shifts over time; (b) an initial T-cell response focused to a restricted segment of the MBP molecule (83-102) that broadened over the course of disease; and (c) persistence of a focused anti-MOG T-cell response. CIS patients who failed to develop CDMS maintained a focused epitope response against two to six MBP epitopes. Most MBP peptide-specific TCLs secreted considerable amounts of IFN-gamma and low amounts of IL-4 and IL-6, whereas anti rhMOG(Igd) peptide-specific TCLs secreted preferentially IL-4 and IL-6. These data raise important issues for the pathogenesis and treatment of multiple sclerosis (MS).