- Award ID(s):
- 1709428
- PAR ID:
- 10184608
- Date Published:
- Journal Name:
- Biomacromolecules
- Volume:
- 20
- Issue:
- 9
- ISSN:
- 1525-7797
- Page Range / eLocation ID:
- 3494 to 3503
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
The morphology of self-assembled block copolymer aggregates is highly dependent on the relative volume fraction of the hydrophobic block. Thus, a dramatic change in the volume fraction of the hydrophobic block can elicit on-demand morphological transitions. Herein, a novel hydrophobic monomer containing a photolabile nitrobenzyl (Nb) protecting group was synthesized and incorporated into a block copolymer with poly(ethylene glycol) methacrylate. This motif allows for the hydrophobic volume fraction of the amphiphilic block copolymer to be dramatically reduced in situ to induce a morphological transition upon irradiation with UV light. Two amphiphilic block copolymers, Nb 94 and Nb 176, with hydrophobic weight fractions of 80% and 86%, respectively, were synthesized and their self-assembly in water studied. Nb 94 assembled into vesicles with R h = 235 nm and underwent a morphological transition after 21 minutes of UV irradiation to spherical micelles with R h = 27 nm, determined by dynamic light scattering and confirmed by transmission electron microscopy. At intermediate irradiation times (14–20 min), Nb 94 vesicles swelled to a larger size, but underwent a morphological transition over the course of hours or days, depending on the exact irradiation time. Nb 176 assembled into large compound vesicles with a hydrodynamic radius ( R h ) of 973 nm, as determined by dynamic light scattering (DLS), which decreased to ca. 700 nm after 300 minutes of UV irradiation with no apparent morphological transition. This study elucidates the mechanism and kinetics of the morphological transitions of block copolymer assemblies induced by a change in the hydrophobic volume fraction of the polymer.more » « less
-
Abstract Numerous biological systems contain vesicle‐like biomolecular compartments without membranes, which contribute to diverse functions including gene regulation, stress response, signaling, and skin barrier formation. Coacervation, as a form of liquid–liquid phase separation (LLPS), is recognized as a representative precursor to the formation and assembly of membrane‐less vesicle‐like structures, although their formation mechanism remains unclear. In this study, a coacervation‐driven membrane‐less vesicle‐like structure is constructed using two proteins, GG1234 (an anionic intrinsically disordered protein) and bhBMP‐2 (a bioengineered human bone morphogenetic protein 2). GG1234 formed both simple coacervates by itself and complex coacervates with the relatively cationic bhBMP‐2 under acidic conditions. Upon addition of dissolved bhBMP‐2 to the simple coacervates of GG1234, a phase transition from spherical simple coacervates to vesicular condensates occurred via the interactions between GG1234 and bhBMP‐2 on the surface of the highly viscoelastic GG1234 simple coacervates. Furthermore, the shell structure in the outer region of the GG1234/bhBMP‐2 vesicular condensates exhibited gel‐like properties, leading to the formation of multiphasic vesicle‐like compartments. A potential mechanism is proposed for the formation of the membrane‐less GG1234/bhBMP‐2 vesicle‐like compartments. This study provides a dynamic process underlying the formation of biomolecular multiphasic condensates, thereby enhancing the understanding of these biomolecular structures.
-
Bro1 stimulates Vps4 to promote intralumenal vesicle formation during multivesicular body biogenesis
Endosomal sorting complexes required for transport (ESCRT-0, -I, -II, -III) execute cargo sorting and intralumenal vesicle (ILV) formation during conversion of endosomes to multivesicular bodies (MVBs). The AAA-ATPase Vps4 regulates the ESCRT-III polymer to facilitate membrane remodeling and ILV scission during MVB biogenesis. Here, we show that the conserved V domain of ESCRT-associated protein Bro1 (the yeast homologue of mammalian proteins ALIX and HD-PTP) directly stimulates Vps4. This activity is required for MVB cargo sorting. Furthermore, the Bro1 V domain alone supports Vps4/ESCRT–driven ILV formation in vivo without efficient MVB cargo sorting. These results reveal a novel activity of the V domains of Bro1 homologues in licensing ESCRT-III–dependent ILV formation and suggest a role in coordinating cargo sorting with membrane remodeling during MVB sorting. Moreover, ubiquitin binding enhances V domain stimulation of Vps4 to promote ILV formation via the Bro1–Vps4–ESCRT-III axis, uncovering a novel role for ubiquitin during MVB biogenesis in addition to facilitating cargo recognition.