This work was supported by grants from Ministerio de Economía y Competitividad-Spain (grant nos MICINN-12-SAF2011-23089 and PI12/01080), European Union (FP7 MicroEnviMet; grant no. UE-08-FP7-HEALTH-2007-A) and the Wellcome Trust (grant no. 079643), as well as by Fundación María Cristina Masaveu Peterson, Fundación Centro Médico de Asturias, Obra Social Cajastur and Fundación Ramón Areces (grant no. SV-12-Areces-1). IUOPA is supported by Obra Social Cajastur and RTICC (Instituto Carlos III, Madrid, Spain). C.L.-O. is an Investigator of the Botín Foundation. J.C. was a recipient of a FEBS Long-term fellowship during part of this work. J.d.l.R. is a recipient of a predoctoral fellowship from Fundación María Cristina Masaveu Peterson.