title: The novel adaptor protein Tks4 (SH3PXD2B) is required for functional podosome formation.
abstract: Metastatic cancer cells have the ability to both degrade and migrate through the extracellular matrix (ECM). Invasiveness can be correlated with the presence of dynamic actin-rich membrane structures called podosomes or invadopodia. We showed previously that the adaptor protein tyrosine kinase substrate with five Src homology 3 domains (Tks5)/Fish is required for podosome/invadopodia formation, degradation of ECM, and cancer cell invasion in vivo and in vitro. Here, we describe Tks4, a novel protein that is closely related to Tks5. This protein contains an amino-terminal Phox homology domain, four SH3 domains, and several proline-rich motifs. In Src-transformed fibroblasts, Tks4 is tyrosine phosphorylated and predominantly localized to rosettes of podosomes. We used both short hairpin RNA knockdown and mouse embryo fibroblasts lacking Tks4 to investigate its role in podosome formation. We found that lack of Tks4 resulted in incomplete podosome formation and inhibited ECM degradation. Both phenotypes were rescued by reintroduction of Tks4, whereas only podosome formation, but not ECM degradation, was rescued by overexpression of Tks5. The tyrosine phosphorylation sites of Tks4 were required for efficient rescue. Furthermore, in the absence of Tks4, membrane type-1 matrix metalloproteinase (MT1-MMP) was not recruited to the incomplete podosomes. These findings suggest that Tks4 and Tks5 have overlapping, but not identical, functions, and implicate Tks4 in MT1-MMP recruitment and ECM degradation.
authors.affiliation: Tumor Microenvironment Program, Burnham Institute for Medical Research, La Jolla, CA 92037, USA.
authors.forename: Matthew D
authors.initials: MD
authors.lastname: Buschman
authors.forename: Paul A
authors.initials: PA
authors.lastname: Bromann
authors.forename: Pilar
authors.initials: P
authors.lastname: Cejudo-Martin
authors.forename: Fang
authors.initials: F
authors.lastname: Wen
authors.forename: Ian
authors.initials: I
authors.lastname: Pass
authors.forename: Sara A
authors.initials: SA
authors.lastname: Courtneidge
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D002460:Cell Line; D021961:Cell Membrane Structures / Q000378:metabolism* / Q000502:physiology / Q000648:ultrastructure; D002465:Cell Movement / Q000502:physiology*; D003001:Cloning, Molecular; D006801:Humans; D050356:Lipid Metabolism; D051379:Mice; D028044:Phosphate-Binding Proteins; D010750:Phosphoproteins / Q000032:analysis / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D010766:Phosphorylation; D017434:Protein Structure, Tertiary
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C114235:Fish protein, mouse; D028044:Phosphate-Binding Proteins; D010750:Phosphoproteins; C541985:Tks4 protein, mouse