Nuclear envelope budding enables large ribonucleoprotein particle export during synaptic Wnt signaling
Department of Neurobiology; Department of Biochemistry and Molecular Pharmacology
Medical Subject Headings
Animals; Drosophila Proteins; Drosophila melanogaster; Frizzled Receptors; Humans; Lamin Type A; Larva; Muscle Fibers, Skeletal; Neuromuscular Junction; Nuclear Envelope; RNA, Messenger; Ribonucleoproteins; Signal Transduction
Life Sciences | Medicine and Health Sciences | Neuroscience and Neurobiology
Localized protein synthesis requires assembly and transport of translationally silenced ribonucleoprotein particles (RNPs), some of which are exceptionally large. Where in the cell such large RNP granules first assemble was heretofore unknown. We previously reported that during synapse development, a fragment of the Wnt-1 receptor, DFrizzled2, enters postsynaptic nuclei where it forms prominent foci. Here we show that these foci constitute large RNP granules harboring synaptic protein transcripts. These granules exit the nucleus by budding through the inner and the outer nuclear membranes in a nuclear egress mechanism akin to that of herpes viruses. This budding involves phosphorylation of A-type lamin, a protein linked to muscular dystrophies. Thus nuclear envelope budding is an endogenous nuclear export pathway for large RNP granules.