RESUMEN
Neurofibromin (NF1) is encoded by the NF1 tumour suppressor gene. Mutations result in a disorder known as Neurofibromatosis Type 1 (NF-1), and patients are often diagnosed due to the presence of unusual pigmentary patterns that include Café au lait macules (CALMs). Little is known about how loss of NF1 results in pigmentary defects in melanocytes. We sought to identify novel NF1 interacting proteins and elucidate the molecular mechanisms underlying the pigmentary defects. The cytoplasmic Dynein Heavy Chain 1 (DHC) was found to interact with NF1 along microtubules in vesicular structures identified to be melanosomes. Our studies suggest that NF1 is involved in melanosomal localization, and that disruptions in NF1-DHC interactions may contribute to the abnormal pigmentary features commonly associated with this debilitating syndrome.
Asunto(s)
Dineínas Citoplasmáticas/metabolismo , Melanocitos/metabolismo , Melanosomas/metabolismo , Neurofibromina 1/metabolismo , Células Cultivadas , Técnicas de Silenciamiento del Gen , Humanos , Recién Nacido , Masculino , Melanocitos/efectos de los fármacos , Melanocitos/ultraestructura , Melanosomas/efectos de los fármacos , Microtúbulos/efectos de los fármacos , Microtúbulos/metabolismo , Neurofibromina 1/antagonistas & inhibidores , Neurofibromina 1/genética , Unión Proteica/efectos de los fármacos , Unión Proteica/genética , ARN Interferente Pequeño/farmacología , Distribución Tisular/efectos de los fármacos , Distribución Tisular/genéticaRESUMEN
Loss-of-function mutations and deletions in the neurofibromin tumor suppressor gene (NF1) cause neurofibromatosis type 1 (NF-1), the most common inherited syndrome of the nervous system in humans, with a birth incidence of 1:3,000. The most visible features of NF-1 are the neoplastic manifestations caused by the loss of Ras-GTPase-activating protein (Ras-GAP) activity mediated through the GAP-related domain (GRD) of neurofibromin (NF1), the protein encoded by NF1. However, the syndrome is also characterized by cognitive dysfunction and a number of developmental abnormalities. The molecular etiology of many of these nonneoplastic phenotypes remains unknown. Here we show that the tubulin-binding domain (TBD) of NF1 is a binding partner of the leucine-rich pentatricopeptide repeat motif-containing (LRPPRC) protein. These two proteins complex with Kinesin 5B, hnRNP A2, Staufen1, and Myelin Basic Protein (MBP) mRNA, likely in RNA granules. This interaction is of interest in that it links NF-1 with Leigh's syndrome, French Canadian variant (LSFC), an autosomal recessive neurodegenerative disorder that arises from mutations in the LRPPRC gene. Our findings provide clues to how loss or mutation of NF1 and LRPPRC may contribute to the manifestations of NF-1 and LSFC.