title: The NHERF1 PDZ2 domain regulates PKA-RhoA-p38-mediated NHE1 activation and invasion in breast tumor cells.
abstract: Understanding the signal transduction systems governing invasion is fundamental for the design of therapeutic strategies against metastasis. Na(+)/H(+) exchanger regulatory factor (NHERF1) is a postsynaptic density 95/disc-large/zona occludens (PDZ) domain-containing protein that recruits membrane receptors/transporters and cytoplasmic signaling proteins into functional complexes. NHERF1 expression is altered in breast cancer, but its effective role in mammary carcinogenesis remains undefined. We report here that NHERF1 overexpression in human breast tumor biopsies is associated with metastatic progression, poor prognosis, and hypoxia-inducible factor-1alpha expression. In cultured tumor cells, hypoxia and serum deprivation increase NHERF1 expression, promote the formation of leading-edge pseudopodia, and redistribute NHERF1 to these pseudopodia. This pseudopodial localization of NHERF1 was verified in breast biopsies and in three-dimensional Matrigel culture. Furthermore, serum deprivation and hypoxia stimulate the Na(+)/H(+) exchanger, invasion, and activate a protein kinase A (PKA)-gated RhoA/p38 invasion signal module. Significantly, NHERF1 overexpression was sufficient to induce these morphological and functional changes, and it potentiated their induction by serum deprivation. Functional experiments with truncated and binding groove-mutated PDZ domain constructs demonstrated that NHERF1 regulates these processes through its PDZ2 domain. We conclude that NHERF1 overexpression enhances the invasive phenotype in breast cancer cells, both alone and in synergy with exposure to the tumor microenvironment, via the coordination of PKA-gated RhoA/p38 signaling.
authors.affiliation: Department of General and Environmental Physiology, University of Bari, 70126 Bari, Italy.
authors.forename: Rosa A
authors.initials: RA
authors.lastname: Cardone
authors.forename: Antonia
authors.initials: A
authors.lastname: Bellizzi
authors.forename: Giovanni
authors.initials: G
authors.lastname: Busco
authors.forename: Edward J
authors.initials: EJ
authors.lastname: Weinman
authors.forename: Maria E
authors.initials: ME
authors.lastname: Dell'Aquila
authors.forename: Valeria
authors.initials: V
authors.lastname: Casavola
authors.forename: Amalia
authors.initials: A
authors.lastname: Azzariti
authors.forename: Anita
authors.initials: A
authors.lastname: Mangia
authors.forename: Angelo
authors.initials: A
authors.lastname: Paradiso
authors.forename: Stephan J
authors.initials: SJ
authors.lastname: Reshkin
mesh_terms: D001943:Breast Neoplasms / Q000378:metabolism* / Q000473:pathology; D027682:Cation Transport Proteins / Q000378:metabolism*; D045744:Cell Line, Tumor; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D005260:Female; D006801:Humans; D000860:Hypoxia / Q000378:metabolism; D066298:In Vitro Techniques; D008875:Middle Aged; D009361:Neoplasm Invasiveness; D010750:Phosphoproteins / Q000737:chemistry / Q000378:metabolism*; D011379:Prognosis; D017434:Protein Structure, Tertiary; D011554:Pseudopodia / Q000378:metabolism / Q000473:pathology; D015398:Signal Transduction; D000074082:Sodium-Hydrogen Exchanger 1; D017923:Sodium-Hydrogen Exchangers / Q000737:chemistry / Q000378:metabolism*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*; D020742:rhoA GTP-Binding Protein / Q000378:metabolism*
chemical_list: D027682:Cation Transport Proteins; D010750:Phosphoproteins; C490998:SLC9A1 protein, human; D000074082:Sodium-Hydrogen Exchanger 1; D017923:Sodium-Hydrogen Exchangers; C093376:sodium-hydrogen exchanger regulatory factor; C066737:RHOA protein, human; D017868:Cyclic AMP-Dependent Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D020742:rhoA GTP-Binding Protein