mInsc coordinates Par3 and NuMA condensates for assembly of the spindle orientation machinery in asymmetric cell division.

As a fundamental process governing the self-renewal and differentiation of stem cells, asymmetric cell division is controlled by several conserved regulators, including the polarity protein Par3 and the microtubule-associated protein NuMA, which orchestrate the assembly and interplay of the Par3/Par6/mInsc/LGN complex at the apical cortex and the LGN/Gαi/NuMA/Dynein complex at the mitotic spindle to ensure asymmetric segregation of cell fate determinants. However, this model, which is well-supported by genetic studies, has been challenged by evidence of competitive interaction between NuMA and mInsc for LGN. Here, the solved crystal structure of the Par3/mInsc complex reveals that mInsc competes with Par6ß for Par3, raising questions about how proteins assemble overlapping targets into functional macromolecular complexes. Unanticipatedly, we discover that Par3 can recruit both Par6ß and mInsc by forming a dynamic condensate through phase separation. Similarly, the phase-separated NuMA condensate enables the coexistence of competitive NuMA and mInsc with LGN in the same compartment. Bridge by mInsc, Par3/Par6ß and LGN/NuMA condensates coacervate, robustly enriching all five proteins both in vitro and within cells. These findings highlight the pivotal role of protein condensates in assembling multi-component signalosomes that incorporate competitive protein-protein interaction pairs, effectively overcoming stoichiometric constraints encountered in conventional protein complexes.

Excessive STAU1 condensate drives mTOR translation and autophagy dysfunction in neurodegeneration.

The double-stranded RNA-binding protein Staufen1 (STAU1) regulates a variety of physiological and pathological events via mediating RNA metabolism. STAU1 overabundance was observed in tissues from mouse models and fibroblasts from patients with neurodegenerative diseases, accompanied by enhanced mTOR signaling and impaired autophagic flux, while the underlying mechanism remains elusive. Here, we find that endogenous STAU1 forms dynamic cytoplasmic condensate in normal and tumor cell lines, as well as in mouse Huntington's disease knockin striatal cells. STAU1 condensate recruits target mRNA MTOR at its 5'UTR and promotes its translation both in vitro and in vivo, and thus enhanced formation of STAU1 condensate leads to mTOR hyperactivation and autophagy-lysosome dysfunction. Interference of STAU1 condensate normalizes mTOR levels, ameliorates autophagy-lysosome function, and reduces aggregation of pathological proteins in cellular models of neurodegenerative diseases. These findings highlight the importance of balanced phase separation in physiological processes, suggesting that modulating STAU1 condensate may be a strategy to mitigate the progression of neurodegenerative diseases with STAU1 overabundance.

A paternal protein facilitates sperm RNA delivery to regulate zygotic development.

Sperm contributes essential paternal factors, including the paternal genome, centrosome, and oocyte-activation signals, to sexual reproduction. However, it remains unresolved how sperm contributes its RNA molecules to regulate early embryonic development. Here, we show that the Caenorhabditis elegans paternal protein SPE-11 assembles into granules during meiotic divisions of spermatogenesis and later matures into a perinuclear structure where sperm RNAs localize. We reconstitute an SPE-11 liquid-phase scaffold in vitro and find that SPE-11 condensates incorporate the nematode RNA, which, in turn, promotes SPE-11 phase separation. Loss of SPE-11 does not affect sperm motility or fertilization but causes pleiotropic development defects in early embryos, and spe-11 mutant males reduce mRNA levels of genes crucial for an oocyte-to-embryo transition or embryonic development. These results reveal that SPE-11 undergoes phase separation and associates with sperm RNAs that are delivered to oocytes during fertilization, providing insights into how a paternal protein regulates early embryonic development.

Overexpression of GLP-1 receptors suppresses proliferation and cytokine release by airway smooth muscle cells of patients with chronic obstructive pulmonary disease via activation of ABCA1.

Glucagon-like peptide-1 (GLP­1) is an important insulin secretagogue that possesses anti­inflammatory effects. GLP­1 receptor (GLP­1R) agonists have been demonstrated to serve a pivotal role in the treatment of obstructive lung diseases, including chronic obstructive pulmonary disease (COPD). However, the specific function and underlying mechanisms of GLP­1R in COPD remain uncertain. The aim of the present study was to investigate the action and underlying mechanisms of GLP­1R in airway smooth muscle (ASM) cells from COPD patients. GLP­1R expression levels were markedly decreased in ASM cells from COPD patients compared with those from healthy controls. ASM cell proliferation and migration, and the levels of the inflammatory cytokines interleukin (IL)­1ß, IL­4, tumor necrosis factor (TNF)­α, and granulocyte­macrophage colony­stimulating factor (GM­CSF) were measured. Transfection of pcDNA3.1­GLP­1R had inhibitory effects on ASM cell proliferation and migration, whereas GLP­1R small interfering (si)RNA reversed these effects. Furthermore, the present study demonstrated that GLP­1R overexpression markedly suppressed IL­1ß, IL­4, TNF­α and GM­CSF levels. GLP­1R overexpression upregulated the expression levels of adenosine triphosphate­binding cassette, subfamily A, member 1 (ABCA1) in ASM cells, and the effects of GLP­1R on cell proliferation and migration, and inflammatory cytokine expression in ASM cells was abolished by siRNA­mediated silencing of ABCA1. The results of the present study suggested that GLP­1R contributes to COPD pathology, potentially via an ABCA1­mediated pathway.