Journal Article

Talin1 phosphorylation activates β1 integrins: a novel mechanism to promote prostate cancer bone metastasis

Lin, S-H, Tien, P-C, Jin, J-K, Huang, C, Song, J H, Cheng, C-J, Gallick, G E

2015

Overview

Talins are adaptor proteins that regulate focal adhesion signaling by conjugating integrins to the cytoskeleton. Talins directly bind integrins and are essential for integrin activation. We previously showed that β1 integrins are activated in metastatic prostate cancer (PCa) cells, increasing PCa metastasis to lymph nodes and bone. However, how β1 integrins are activated in PCa cells is unknown. In this study, we identified a novel mechanism of β1 integrin activation. Using knockdown experiments, we first demonstrated that talin1, but not talin2, is important in β1 integrin activation. We next showed that talin1 S425 phosphorylation, but not total talin1 expression, correlates with metastatic potential of PCa cells. Expressing a non-phosphorylatable mutant, talin1 S425A , in talin1-silenced PC3-MM2 and C4-2B4 PCa cells, decreased activation of β1 integrins, integrin-mediated adhesion, motility and increased the sensitivity of the cells to anoikis. In contrast, reexpression of the phosphorylation-mimicking mutant talin1 S425D led to increased β1 integrin activation and generated biologic effects opposite to talin1 S425A expression. In the highly metastatic PC3-MM2 cells, expression of a non-phosphorylatable mutant, talin1 S425A , in talin1-silenced PC3-MM2 cells, abolished their ability to colonize in the bone following intracardiac injection, while reexpression of phosphorylation-mimicking mutant talin1 S425D restored their ability to metastasize to bone. Immunohistochemical staining demonstrated that talin S425 phosphorylation is significantly increased in human bone metastases when compared with normal tissues, primary tumors or lymph node metastases. We further showed that p35 expression, an activator of Cdk5, and Cdk5 activity were increased in metastatic tumor cells, and that Cdk5 kinase activity is responsible for talin1 phosphorylation and subsequent β1 integrin activation. Together, our study reveals Cdk5-mediated phosphorylation of talin1 leading to β1 integrin activation is a novel mechanism that increases metastatic potential of PCa cells.

• Publisher: Nature Publishing Group UK,Nature Publishing Group
• Subject: 631/67/322/803 / 631/67/589/466 / 631/80/304 / 631/80/86 / Adaptor proteins / Adaptor Proteins, Signal Transducing - biosynthesis / Adaptor Proteins, Signal Transducing - metabolism / Animals / Anoikis / Anoikis - genetics / Apoptosis / Bone cancer / Bone Neoplasms - secondary / Bone tumors / Carrier proteins / Cell activation / Cell Adhesion / Cell Biology / Cell Cycle Proteins - biosynthesis / Cell Cycle Proteins - metabolism / Cell Line, Tumor / Cell Movement / Complications and side effects / Cyclin-dependent kinase 5 / Cyclin-Dependent Kinase 5 - metabolism / Cytoskeleton / Development and progression / Enzyme Activation / Focal Adhesions - metabolism / Genetic aspects / Health aspects / Human Genetics / Humans / Integrin beta1 - metabolism / Integrins / Internal Medicine / Kinases / Lymph nodes / Lymphatic Metastasis / Male / Medicine / Medicine & Public Health / Metastases / Metastasis / Mice / Mimicry / Mutants / Oncology / original-article / Phosphorylation / Prostate - pathology / Prostate cancer / Prostatic Neoplasms - pathology / Protein Binding / RNA Interference / RNA, Small Interfering / Talin / Talin - biosynthesis / Talin - genetics / Talin - metabolism / Tumor cells