Par-1 Regulates Tissue Growth by Influencing Hippo Phosphorylation Status and Hippo-Salvador Association
Figure 2
Overexpression of Par-1 triggers tissue overgrowth and inactivates Hpo signaling in a kinase-dependent manner.
(A) Par-1 enhances the transcriptional activity of the Yki-Sd complex in vitro. S2 cells were transfected with the indicated constructs and the luciferase reporter genes. 48 h after transfection, the cell lysates were harvested and subjected to a dual luciferase assay. Note that Par-1 activates the 3×Sd2-Luc reporter compared with the control. All of these data were represented as the mean ± SEM. **p<0.01. **p<0.001. (B–C″) Par-1, but not Par-1-KD, synergizes with Yki to trigger tissue overgrowth. Side view of D. melanogaster adult eyes: wild-type (B); eyes expressing two copies of UAS-Par-1 (B′), two copies of UAS-Par-1-KD (B″) or UAS-Yki (C); or eyes co-expressing UAS-Yki and two copies of UAS-Par-1 (C′) or UAS-Yki and two copies of UAS-Par-1-KD (C″), driven by GMR-Gal4. (D–E″) Par-1, but not Par-1-KD, induces Drosophila wing overgrowth. Dorsal view (D–D″) or side view (E–E″) of the control wings (D, E), wings expressing two copies of UAS-Par-1 (D′, E′), or wings expressing two copies of UAS-Par-1-KD (D″, E″), with MS1096. The red dashed line indicated the size of the control wings. The relative wing size was quantified using the unpaired t-test (D′″). The results represented the mean ± SEM. *** means p<0.001 (n>6) for each genotype. Note that the adult wings were bent down in flies that overexpressed Par-1. This phenotype was not observed in the flies that overexpressed Par-1-KD. (F–I′) Par-1, but not Par-1-KD, promotes the Hpo pathway-responsive gene expression. Drosophila discs containing flip-out clones expressing UAS-Myc-Par-1 or UAS-Myc-Par-1-KD driven by act>CD2>Gal4 were dissected and immunostained with the indicated antibodies. Cells expressing UAS-Myc-Par-1 or UAS-Myc-Par-1-KD transgenes were labeled by Myc tag (indicated by arrows). Note the upregulation of diap1 and ex transcription via ectopic Par-1 expression. Par-1-KD was incapable of inducing diap1 and ex expression.