RESUMO
Enhanced secretion of tumorigenic effector proteins is a feature of malignant cells. The molecular mechanisms underlying this feature are poorly defined. We identify PITPNC1 as a gene amplified in a large fraction of human breast cancer and overexpressed in metastatic breast, melanoma, and colon cancers. Biochemical, molecular, and cell-biological studies reveal that PITPNC1 promotes malignant secretion by binding Golgi-resident PI4P and localizing RAB1B to the Golgi. RAB1B localization to the Golgi allows for the recruitment of GOLPH3, which facilitates Golgi extension and enhanced vesicular release. PITPNC1-mediated vesicular release drives metastasis by increasing the secretion of pro-invasive and pro-angiogenic mediators HTRA1, MMP1, FAM3C, PDGFA, and ADAM10. We establish PITPNC1 as a PI4P-binding protein that enhances vesicular secretion capacity in malignancy.
Assuntos
Complexo de Golgi/metabolismo , Proteínas de Membrana Transportadoras/metabolismo , Proteínas rab1 de Ligação ao GTP/metabolismo , Animais , Neoplasias da Mama/metabolismo , Linhagem Celular , Linhagem Celular Tumoral , Neoplasias do Colo/metabolismo , Feminino , Humanos , Melanoma/metabolismo , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos NOD , Camundongos SCIDRESUMO
Altered abundance of phosphatidyl inositides (PIs) is a feature of cancer. Various PIs mark the identity of diverse membranes in normal and malignant cells. Phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) resides predominantly in the plasma membrane, where it regulates cellular processes by recruiting, activating, or inhibiting proteins at the plasma membrane. We find that PTPRN2 and PLCß1 enzymatically reduce plasma membrane PI(4,5)P2 levels in metastatic breast cancer cells through two independent mechanisms. These genes are upregulated in highly metastatic breast cancer cells, and their increased expression associates with human metastatic relapse. Reduction in plasma membrane PI(4,5)P2 abundance by these enzymes releases the PI(4,5)P2-binding protein cofilin from its inactive membrane-associated state into the cytoplasm where it mediates actin turnover dynamics, thereby enhancing cellular migration and metastatic capacity. Our findings reveal an enzymatic network that regulates metastatic cell migration through lipid-dependent sequestration of an actin-remodeling factor.
