Dia-Interacting Protein (DIP) Imposes Migratory Plasticity in mDia2-Dependent Tumor Cells in Three-Dimensional Matrices

Abstract

Tumor cells rely upon membrane pliancy to escape primary lesions and invade secondary metastatic sites. This process relies upon localized assembly and disassembly cycles of F-actin that support and underlie the plasma membrane. Dynamic actin generates both spear-like and bleb structures respectively characterizing mesenchymal and amoeboid motility programs utilized by metastatic cells in three-dimensional matrices. The molecular mechanism and physiological trigger(s) driving membrane plasticity are poorly understood. mDia formins are F-actin assembly factors directing membrane pliancy in motile cells. mDia2 is functionally coupled with its binding partner DIP, regulating cortical actin and inducing membrane blebbing in amoeboid cells. Here we show that mDia2 and DIP co-tether to nascent blebs and this linkage is required for bleb formation. DIP controls mesenchymal/amoeboid cell interconvertability, while CXCL12 induces assembly of mDia2:DIP complexes to bleb cortices in 3D matrices. These results demonstrate how DIP-directed mDia2-dependent F-actin dynamics regulate morphological plasticity in motile cancer cells.

mDia2 and CXCL12/CXCR4 chemokine signaling intersect to drive tumor cell amoeboid morphological transitions

“…We previously showed CXCL12 initiates mDia2-dependent non-apoptotic blebbing in MDA-MB-231 cells in 2D matrices and within 3D collagen gels, and causes cells to adopt an elongated phenotype[11]. This resembled phenotypes observed upon treatment with a functional mDia FH2 domain inhibitor, SMIFH2.…”

“…1B). CXCL12 initiated blebbing within an hour of treatment [11], with mDia2 and CXCR4 distinctly localizing in blebs at the cell periphery (Fig. 1C).…”

“…This disrupts the cortical actin cytoskeleton. DIP-mediated mDia2 inhibition converts elongated, mesenchymal cancer cells to rounded amoeboid morphologies enriched in non-apoptotic membrane blebs which undergo expansion/retraction cycles, typically without detachment [10, 11]. Amoeboid morphological shifts can underlie migration programs that are typically independent of integrins or proteolytic extracellular matrix degradation [12].…”

“…The chemokine CXCL12 promotes both DIP:mDia2 axis assembly and subsequent non-apoptotic amoeboid blebbing [10, 11]. In breast, prostate and lung cancers, CXCL12 promotes metastasis to distal sites that express high chemokine levels [15, 16].…”

Trading in your spindles for blebs: the amoeboid tumor cell phenotype in prostate cancer

“…Overexpression of the Formin-like protein 2 evokes MAT,78 and FHOD1 promotes membrane blebbing in conjunction with ROCK1 and Src79, while Dia1 promotes bleb-based cell motility through the GEF LARG 80. Eisenmann and colleagues demonstrated that inhibition of mDia2, through binding to DIA-interacting protein (DIP), similarly induces an amoeboid transition 8182. Interestingly, the DIAPH3 locus encodes multiple splice variants that differentially impact actin dynamics and membrane blebbing 83.…”