Journal of Cell Biology最新文献

Adherens junctions regulate tissue architecture, mediating robust yet dynamic cell-cell adhesion and, via cytoskeletal linkage, allowing cells to change shape and move. Adherens junctions contain thousands of molecules linked by multivalent interactions of folded protein domains and intrinsically disordered regions (IDRs). One key challenge is defining mechanisms conferring robust linkage and mechanosensing. Drosophila Canoe and mammalian Afadin provide superb entry points to explore how their complex protein structures and shared IDRs enable function. We combined genetic, cell biological, and biochemical tools to define how Canoe's IDR functions during morphogenesis. Unlike many of Canoe's folded domains, the proximal IDR is critical for junctional localization, mechanosensing, and function. In its absence, the mutant protein localizes to nuclei. We took the IDR apart, identifying two conserved stickers that directly bind F-actin, separated by less-conserved spacers. Surprisingly, while mutants lacking the IDR die as embryos with morphogenesis defects, no IDR subregion is essential for viability. Instead, stickers and spacers act combinatorially to ensure localization, mechanosensing, and function.

Endo-lysosomes are considered acidic Ca2+ stores, but direct measurements of luminal Ca2+ within them are limited. Here, we report that the Ca2+-sensitive luminescent protein aequorin does not reconstitute with its cofactor at highly acidic pH but that a significant fraction of the probe is functional within a mildly acidic compartment when targeted to the endo-lysosomal system. We leveraged this probe (ELGA) to report Ca2+ dynamics in this compartment. We show that Ca2+ uptake is ATP-dependent and sensitive to blockers of ER Ca2+ pumps. We find that the Ca2+ mobilizing messenger IP3 evokes robust luminal responses in wild-type cells, but not in IP3R knockout cells. Responses were comparable to those evoked by activation of the endo-lysosomal ion channels TPCs and TRPMLs. Stimulation with IP3-forming agonists also mobilized the store in intact cells. Super-resolution microscopy analysis was consistent with the presence of IP3Rs within the endo-lysosomal system. Our data reveal a physiologically relevant, IP3-sensitive store of Ca2+ within the endo-lysosomal system.

Peroxisome biogenesis in humans is not governed by PPARα, overturning a paradigm established in rodents. PPARα agonists fail to induce canonical peroxisomal genes, and functional response elements are absent from key promoters. Human peroxisomes nonetheless expand through PPAR-independent pathways, positioning them as organelles tuned to immunometabolic and redox demands and redefining strategies for therapeutic intervention.

Centrosomes are highly dynamic organelles, and maintaining their stability is crucial for spindle pole integrity and bipolar spindle formation. Centrosomes consist of a pair of centrioles surrounded by the PCM. In Caenorhabditis elegans, interactions between the scaffold protein SPD-5 and kinase PLK-1 are essential for PCM formation. However, how PCM stability is established and maintained remains unclear. We address this by analyzing the function of PCMD-1, a protein mainly localizing to centrioles. We show that CDK-1 primes PCMD-1 for PLK-1 phosphorylation. Mutations in PLK-1 docking sites abolish PCMD-1 phosphorylation and SPD-5 binding in vitro and destabilize the PCM scaffold in vivo. As a result, microtubule-pulling forces cannot be relayed to centrioles, delaying their separation. Our findings reveal that PCMD-1 is critical for PCM stability and timely centriole separation during PCM disassembly. We propose that PCMD-1 initiates scaffold assembly by biasing the PCM core toward intrinsic order, acting as a seed that propagates throughout the scaffold to ensure structural integrity.