title: Talin1 phosphorylation activates β1 integrins: a novel mechanism to promote prostate cancer bone metastasis.
abstract: 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.
authors.affiliation: 1] Department of Genitourinary Medical Oncology, Unit 18-4, David H. Koch Center for Applied Research of Genitourinary Cancers, The University of Texas M. D. Anderson Cancer Center, Houston, TX, USA [2] The Program in Cancer Metastasis, The University of Texas Graduate School of Biomedical Sciences at Houston, Houston, TX, USA.
authors.forename: J-K
authors.initials: JK
authors.lastname: Jin
authors.affiliation: Department of Genitourinary Medical Oncology, Unit 18-4, David H. Koch Center for Applied Research of Genitourinary Cancers, The University of Texas M. D. Anderson Cancer Center, Houston, TX, USA.
authors.forename: P-C
authors.initials: PC
authors.lastname: Tien
authors.affiliation: Department of Pathology, College of Medicine, Taipei Medical University, Taipei, Taiwan.
authors.forename: C-J
authors.initials: CJ
authors.lastname: Cheng
authors.affiliation: Department of Genitourinary Medical Oncology, Unit 18-4, David H. Koch Center for Applied Research of Genitourinary Cancers, The University of Texas M. D. Anderson Cancer Center, Houston, TX, USA.
authors.forename: J H
authors.initials: JH
authors.lastname: Song
authors.affiliation: Department of Molecular and Biomedical Pharmacology, University of Kentucky, Lexington, KY, USA.
authors.forename: C
authors.initials: C
authors.lastname: Huang
authors.affiliation: 1] Department of Genitourinary Medical Oncology, Unit 18-4, David H. Koch Center for Applied Research of Genitourinary Cancers, The University of Texas M. D. Anderson Cancer Center, Houston, TX, USA [2] The Program in Cancer Metastasis, The University of Texas Graduate School of Biomedical Sciences at Houston, Houston, TX, USA [3] Department of Translational Molecular Pathology, Unit 89, David H. Koch Center for Applied Research of Genitourinary Cancers, The University of Texas M. D. Anderson Cancer Center, Houston, TX, USA.
authors.forename: S-H
authors.initials: SH
authors.lastname: Lin
authors.affiliation: 1] Department of Genitourinary Medical Oncology, Unit 18-4, David H. Koch Center for Applied Research of Genitourinary Cancers, The University of Texas M. D. Anderson Cancer Center, Houston, TX, USA [2] The Program in Cancer Metastasis, The University of Texas Graduate School of Biomedical Sciences at Houston, Houston, TX, USA.
authors.forename: G E
authors.initials: GE
authors.lastname: Gallick
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000096:biosynthesis / Q000378:metabolism*; D000818:Animals; D023102:Anoikis / Q000235:genetics; D001859:Bone Neoplasms / Q000556:secondary*; D002448:Cell Adhesion; D018797:Cell Cycle Proteins / Q000096:biosynthesis / Q000378:metabolism*; D045744:Cell Line, Tumor; D002465:Cell Movement; D051360:Cyclin-Dependent Kinase 5 / Q000378:metabolism*; D004789:Enzyme Activation; D022001:Focal Adhesions / Q000378:metabolism; D006801:Humans; D019012:Integrin beta1 / Q000378:metabolism*; D008207:Lymphatic Metastasis; D008297:Male; D051379:Mice; D010766:Phosphorylation; D011467:Prostate / Q000473:pathology; D011471:Prostatic Neoplasms / Q000473:pathology; D011485:Protein Binding; D034622:RNA Interference; D034741:RNA, Small Interfering; D016608:Talin / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C500695:CDCA5 protein, human; D018797:Cell Cycle Proteins; D019012:Integrin beta1; D034741:RNA, Small Interfering; C518832:TLN1 protein, human; C436513:TLN2 protein, human; D016608:Talin; D051360:Cyclin-Dependent Kinase 5; C495905:CDK5 protein, human