RESUMEN
Dynamic rearrangements of the F-actin cytoskeleton are a hallmark of tumor metastasis. Thus, proteins that govern F-actin rearrangements are of major interest for understanding metastasis and potential therapies. We hypothesized that the unique F-actin binding and bundling protein SWAP-70 contributes importantly to metastasis. Orthotopic, ectopic, and short-term tail vein injection mouse breast and lung cancer models revealed a strong positive dependence of lung and bone metastasis on SWAP-70. Breast cancer cell growth, migration, adhesion, and invasion assays revealed SWAP-70's key role in these metastasis-related cell features and the requirement for SWAP-70 to bind F-actin. Biophysical experiments showed that tumor cell stiffness and deformability are negatively modulated by SWAP-70. Together, we present a hitherto undescribed, unique F-actin modulator as an important contributor to tumor metastasis.
Asunto(s)
Actinas , Neoplasias de la Mama , Neoplasias Pulmonares , Proteínas de Microfilamentos , Metástasis de la Neoplasia , Animales , Actinas/metabolismo , Ratones , Humanos , Femenino , Línea Celular Tumoral , Neoplasias de la Mama/patología , Neoplasias de la Mama/metabolismo , Neoplasias de la Mama/genética , Neoplasias Pulmonares/metabolismo , Neoplasias Pulmonares/patología , Neoplasias Pulmonares/genética , Neoplasias Pulmonares/secundario , Proteínas de Microfilamentos/metabolismo , Proteínas de Microfilamentos/genética , Movimiento Celular/genética , Citoesqueleto de Actina/metabolismo , Proliferación Celular/genética , Adhesión Celular/genética , Unión ProteicaRESUMEN
F-actin binding and bundling are crucial to a plethora of cell processes, including morphogenesis, migration, adhesion and many others. SWAP-70 was recently described as an in vitro F-actin-binding and -bundling protein. Fluorescence cross-correlation spectroscopy measurements with purified recombinant SWAP-70 confirmed that it forms stable oligomers that facilitate F-actin bundling. However, it remained unclear how SWAP-70 oligomerization and F-actin binding are controlled in living cells. We addressed this by biophysical approaches, including seFRET, FACS-FRET and FLIM-FRET. PIP3-mediated association with the cytoplasmic membrane and non-phosphorylated Y426 are required for SWAP-70 to dimerize and to bind F-actin. The dimerization region was identified near the C terminus where R546 is required for dimerization and, thus, F-actin bundling. The in vitro and in vivo data presented here reveal the functional relationship between the cytoplasm-to-membrane translocation and dimerization of SWAP-70, and F-actin binding and bundling, and demonstrate that SWAP-70 is a finely controlled modulator of membrane-proximal F-actin dynamics.This article has an associated First Person interview with the first author of the paper.