External push and internal pull forces recruit curvature-sensing N-BAR domain proteins to the plasma membrane

N-BAR-domain-containing proteins regulate membrane dynamics, as they stabilize curved membrane topologies, but whether they primarily sense or generate curvature has remained unclear. Galic, Meyer and colleagues now report that N-BAR proteins accumulate at highly curved membrane areas. Many of the more than 20 mammalian proteins with N-BAR domains 1 , 2 control cell architecture 3 and endocytosis 4 , 5 by associating with curved sections of the plasma membrane 6 . It is not well understood whether N-BAR proteins are recruited directly by processes that mechanically curve the plasma membrane or indirectly by plasma-membrane-associated adaptor proteins that recruit proteins with N-BAR domains that then induce membrane curvature. Here, we show that externally induced inward deformation of the plasma membrane by cone-shaped nanostructures (nanocones) and internally induced inward deformation by contracting actin cables both trigger recruitment of isolated N-BAR domains to the curved plasma membrane. Markedly, live-cell imaging in adherent cells showed selective recruitment of full-length N-BAR proteins and isolated N-BAR domains to plasma membrane sub-regions above nanocone stripes. Electron microscopy confirmed that N-BAR domains are recruited to local membrane sites curved by nanocones. We further showed that N-BAR domains are periodically recruited to curved plasma membrane sites during local lamellipodia retraction in the front of migrating cells. Recruitment required myosin-II-generated force applied to plasma-membrane-connected actin cables. Together, our results show that N-BAR domains can be directly recruited to the plasma membrane by external push or internal pull forces that locally curve the plasma membrane.