The formins FHOD1 and INF2 regulate inter- and intra-structural contractility of podosomes

• DOI: 10.1242/jcs.177691
• Publication Date: 2015-12-01T02:40:19Z
• Authors: Linda Panzer; Leona Trübe; Matthias Klose; Ben Joosten; Johan Slotman; Alessandra Cambi; Stefan Linder
• Keywords: Fetal Proteins; 0303 health sciences; Macrophages; Microfilament Proteins; Formins; Nuclear Proteins; EMC MM-03-24-01; Actins; Extracellular Matrix; 03 medical and health sciences; Radboudumc 2: Cancer development and immune defence RIMLS: Radboud Institute for Molecular Life Sciences; Podosomes; Humans; Cells, Cultured

Podosomes are actin-rich adhesion structures that depend on Arp2/3 complex-based actin nucleation. We now report the identification of the formins FHOD1 and INF2 as novel components and additional actin-based regulators of podosomes in primary human macrophages. FHOD1 surrounds the podosome core and is also present at podosome-connecting cables, whereas INF2 localizes at the podosome cap structure. Using a variety of microscopy-based methods, including a semiautomated podosome reformation assay, measurement of podosome oscillations, FRAP analysis of single podosomes, and structured illumination microscopy, both formins were found to regulate different aspects of podosome-associated contractility, with FHOD1 mediating actomyosin contractility between podosomes, and INF2 regulating contractile events at individual podosomes. Moreover, INF2 was found to be a critical regulator of podosome de novo formation and size. Collectively, we identify FHOD1 and INF2 as novel regulators of inter- and intra-structural contractility of podosomes. Podosomes thus present as one of the few currently identified structures, which depend on the concerted activity of both Arp2/3 complex and specific formins and may serve as a model system for the analysis of complex actin architectures in cells.