In Vivo Formation of Vacuolated Multi-phase Compartments Lacking Membranes.
2016; 16 (5): 1228-1236
Eukaryotic cells contain membrane-less organelles, including nucleoli and stress granules, that behave like liquid droplets. Such endogenous condensates often have internal substructure, but how this is established in the absence of membrane encapsulation remains unclear. We find that the N- and C-terminal domains of TDP43, a heterogeneous nuclear ribonucleoprotein implicated in neurodegenerative diseases, are capable of driving the formation of sub-structured liquid droplets in vivo. These droplets contain dynamic internal "bubbles" of nucleoplasm, reminiscent of membrane-based multi-vesicular endosomes. A conserved sequence embedded within the intrinsically disordered region (IDR) of TDP43 promotes the formation of these multi-phase assemblies. Disease-causing point mutations in the IDR can change the propensity to form bubbles, protein dynamics within the phase, or phase-environment exchange rates. Our results show that a single IDR-containing protein can nucleate the assembly of compartmentalized liquid droplets approximating the morphological complexity of membrane-bound organelles.
View details for DOI 10.1016/j.celrep.2016.06.088
View details for PubMedID 27452472
View details for PubMedCentralID PMC4972689
Nup98 FG domains from diverse species spontaneously phase-separate into particles with nuclear pore-like permselectivity
Nuclear pore complexes (NPCs) conduct massive transport mediated by shuttling nuclear transport receptors (NTRs), while keeping nuclear and cytoplasmic contents separated. The NPC barrier in Xenopus relies primarily on the intrinsically disordered FG domain of Nup98. We now observed that Nup98 FG domains of mammals, lancelets, insects, nematodes, fungi, plants, amoebas, ciliates, and excavates spontaneously and rapidly phase-separate from dilute (submicromolar) aqueous solutions into characteristic 'FG particles'. This required neither sophisticated experimental conditions nor auxiliary eukaryotic factors. Instead, it occurred already during FG domain expression in bacteria. All Nup98 FG phases rejected inert macromolecules and yet allowed far larger NTR cargo complexes to rapidly enter. They even recapitulated the observations that large cargo-domains counteract NPC passage of NTR⋅cargo complexes, while cargo shielding and increased NTR⋅cargo surface-ratios override this inhibition. Their exquisite NPC-typical sorting selectivity and strong intrinsic assembly propensity suggest that Nup98 FG phases can form in authentic NPCs and indeed account for the permeability properties of the pore.
View details for DOI 10.7554/eLife.04251
View details for Web of Science ID 000347420600002
View details for PubMedID 25562883