Full activity of the deleted in liver cancer 1 (DLC1) tumor suppressor depends on an LD-like motif that binds talin and focal adhesion kinase (FAK)

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 108; no. 41; pp. 17129 - 17134
• Main Authors: Li, Guorong, Du, Xiaoli, Vass, William C, Papageorge, Alex G, Lowy, Douglas R, Qian, Xiaolan
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 11.10.2011; National Acad Sciences
• Subjects: adhesion; Amino Acid Motifs; Amino Acid Sequence; Amino Acid Substitution; Amino acids; Animals; Base Sequence; Binding Sites; Bioassays; Biological Sciences; Cancer; Cell culture techniques; Cell growth; Cell Line, Tumor; Cell lines; Focal Adhesion Kinase 1 - metabolism; Focal adhesions; GTPase-Activating Proteins - antagonists & inhibitors; GTPase-Activating Proteins - chemistry; GTPase-Activating Proteins - genetics; GTPase-Activating Proteins - metabolism; guanosinetriphosphatase; HEK293 Cells; Humans; Liver cancer; liver neoplasms; Mice; Mice, Inbred NOD; Mice, SCID; Microfilament Proteins - metabolism; Multiprotein Complexes - chemistry; Multiprotein Complexes - metabolism; mutants; Mutation; NIH 3T3 Cells; Proteins; Recombinant Fusion Proteins - chemistry; Recombinant Fusion Proteins - genetics; Recombinant Fusion Proteins - metabolism; RNA, Small Interfering - genetics; Sequence Deletion; Small interfering RNA; talin; Talin - chemistry; Talin - genetics; Talin - metabolism; Tensins; Transfection; tumor suppressor genes; Tumor Suppressor Proteins - antagonists & inhibitors; Tumor Suppressor Proteins - chemistry; Tumor Suppressor Proteins - genetics; Tumor Suppressor Proteins - metabolism; Tumors
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1112122108

The deleted in liver cancer 1 (DLC1) tumor suppressor gene, which is frequently inactivated in cancer, encodes a Rho-GAP (GTPase activating protein) focal adhesion protein whose negative regulation of Rho-GTPases is necessary but not sufficient for its full tumor suppressor activity. Here, we report that DLC1 forms a complex with two prooncogenic focal adhesion proteins, talin and the focal adhesion kinase (FAK). We identified an 8-aa sequence (residues 469LDDILYHV476) in DLC1 and designated it an LD-like motif, because it shares homology with the LD motifs of paxillin. This motif was necessary for DLC1 binding to talin and FAK, because a DLC1 mutant, from which six of the residues have been deleted, and another mutant carrying amino acid substitutions in three of the residues are deficient for binding both proteins and localization of DLC1 to focal adhesions. FAK binding was independent of talin and vice versa. In bioassays, both DLC1 mutants were less active than wild-type (WT) DLC1, although the ability of the mutants to negatively regulate overall Rho-GTP was not impaired. We conclude that the LD-like motif, which binds talin and FAK, is required for the full tumor suppressor activity of DLC1 and contributes to the association of DLC1 with focal adhesions.