Figure 1

LKB1 expression induces actin filament assembly in HeLa-S3 cells. HeLa-S3 cells were transfected with different myc-tagged LKB1 constructs cloned into the pRK5 expression plasmid. Cells were fixed and stained with anti-myc antibody and fluorescent phalloidin to visualize filamentous actin. A. Control cells expressing an empty pRK5-myc vector displayed mainly cortical actin filaments and a few thin actin filaments across the cell bodies. B-E. Expression of wild type (B and C), or kinase dead (D194A) myc-tagged LKB1 (D and E) led to actin filament formation in HeLa-S3 cells. Both wild type and kinase dead LKB1 were found in the nucleus and in the cytoplasm. F, G. LKB1 C-terminus does not induce actin filaments. H. LKB1 domain structure and constructs used in the paper. Critical amino acids are indicated. I. Quantification of LKB1 effect on actin filament (stress fiber) formation. Expressing cells were scored for stress fiber formation (actin filament bundles across cell bodies). Scale bar = 20 μm.