Molecular mechanisms of podosome dynamics and macrophage invasion

• Applicant: Professor Dr. Stefan Linder
• Subject Area: Cell Biology
• Term: from 2007 to 2017
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 61191235

Podosomes are a specialized form of cell-matrix adhesions that are consitutively formed in cells of the monocytic lineage including macrophages. Podosomes are multifunctional organelles that combine several key functions of invasive cells, including adhesion, matrix degradation and mechanosensing and are thus believed to be decisive for invasive cell migration in both health and disease.Podosomes consist of various substructures, including an actin-rich core, a ring structure of plaque proteins and a newly discovered cap structure on top of the actin-rich core. Of note, podosomes are highly dynamic structures that critically depend on fine-tuned spatiotemporal control of actin turnover. This project is focused on the roles of three newly identified, actin-associated podosome components (Swiprosin-1, SKAP-2 and Scinderin) in podosome formation, coordination, architecture and turnover. As two of these proteins (SKAP-2, Swiprosin-1) are part of the newly identified cap structure of podosomes, particular emphasis will be placed on elucidating their roles in regulation of the cap strucuture, their possible interaction with previously identified cap components, and their potential impact on the regulation of cap structure-generated actin cables, which allow the coordination of individual podosomes into higher-ordered groups. Podosomes are known to be Ca2+-sensitive structures, with the underlying mechanism(s) being most-ly unclear. As both Scinderin and Swiprosin-1 are Ca2+-regulated proteins, elucidation of their role, in particular the potential actin severing function of Scinderin in the podosome core, will provide im-portant new insights into the respective regulatory pathways. Moreover, determination of the influence of specific Src kinases on Swiprosin-1 and SKAP-2 functions at podosomes will deepen the under-standing of the crucial dependence of podosomes on Src kinase signaling.We will study the roles of Swiprosin-1, SKAP-2 and Scinderin using a combination of established methods and newly applied ones including micropatterned substrates and cryoelectron tomography. Moreover, we will determine the impact of these proteins on podosome formation, architecture and function also in 3D settings, as well as on proteolytic invasion of macrophages into 3D collagen gels.

• DFG Programme: Research Grants