du Maine Xavier, Gu Chenghua
Department of Neurobiology, Howard Hughes Medical Institute, Harvard Medical School, Boston, MA 02115, USA.
bioRxiv. 2025 Mar 13:2025.03.10.642437. doi: 10.1101/2025.03.10.642437.
Canonical Wnt signaling is essential for blood-brain barrier (BBB) development and maintenance. However, the subcellular mechanisms underlying this critical regulation have remained elusive. In this study, we use a physiological paradigm examining an early phase of acutely attenuated canonical Wnt signaling in adult brain endothelial cells (ECs) to investigate how the pathway regulates BBB integrity. Following canonical Wnt signaling attenuation via EC-specific knockout of β-catenin, we find that there is increased transcytosis in brain ECs, including a striking diversity of morphologically distinct vesicles, indicating multiple pathways are involved. In addition, we find that although the molecular composition of tight junctions (TJs) is altered following canonical Wnt signaling attenuation, such that Claudin-5 and ZO-1 expression is downregulated, TJs remain impermeable to molecules as small as 1.9 kDa. These findings reveal previously underappreciated role of Wnt signaling in regulating brain EC transcytosis and help illuminate subcellular mechanisms of BBB maintenance in adulthood, which is crucial for improving delivery of therapeutics to the brain.
经典Wnt信号通路对于血脑屏障（BBB）的发育和维持至关重要。然而，这种关键调节作用背后的亚细胞机制仍不清楚。在本研究中，我们采用一种生理学范式，研究成年脑内皮细胞（ECs）中急性减弱的经典Wnt信号通路的早期阶段，以探究该信号通路如何调节血脑屏障的完整性。通过内皮细胞特异性敲除β-连环蛋白来减弱经典Wnt信号通路后，我们发现脑内皮细胞的转胞吞作用增强，包括形态各异的囊泡种类显著增多，这表明涉及多种途径。此外，我们发现，尽管经典Wnt信号通路减弱后紧密连接（TJs）的分子组成发生了改变，导致Claudin-5和ZO-1的表达下调，但紧密连接对小至1.9 kDa的分子仍具有屏障作用。这些发现揭示了Wnt信号通路在调节脑内皮细胞转胞吞作用方面此前未被充分认识的作用，并有助于阐明成年期血脑屏障维持的亚细胞机制，这对于改善治疗药物向脑内的递送至关重要。
