We are interested in the epithelial function involving signal transduction, membrane protein trafficking and ion channel regulation, using the tools of cell and molecular biology, biochemistry, and biophysics.

Dennis A. Ausiello, MD 
Professor of Medicine 
55 Fruit Street, GRB 740
Boston, MA 02114
Phone: (617) 726-5660
Fax: (617) 724-7441
Email: dausiello@partners.org

 

Studies in signal transduction involve the molecular biology of the vasopressin receptor and guanine nucleotide regulatory (G) protein associated with various membranes in polarized epithelia. Ongoing work involves defining the structure-function relationships among the various a subunits of G proteins and the differential membrane targeting of homologous a subunits. These studies have been facilitated by the development of stably transfected cell models incorporating the genes for a subunits of G proteins coupled to inducible promoters. Developmental and regulatory studies of the a subunits have shown that they are selectively targeted to the apical and basolateral plasma membranes or to intracellular membranes such as the Golgi complex.

Studies of the cell biology of membrane proteins involve the regulation of vesicle trafficking of the vasopressin - sensitive water channel as well as secretary vesicles containing proteoglycans. Emphasis is on signal transduction mechanisms involved in regulatory and constitutive endo- and exocytosis. We have identified monomeric and heterotrimeric G proteins involved in these pathways.

The study of the regulation of ion channels, particularly Na and Cl conductive pathways in the apical membranes of epithelia, has resulted in the identification of the components of a signal transduction pathway involving G proteins, phospholipases, lipoxygenases and actin filaments. This novel signal transduction pathway in the apical membrane is distinct from classical signal transduction at the basolateral membrane of epithelia and can be studied utilizing the patch clamp technique. Cell models stably transfected with normal and mutant G proteins targeted to the apical membrane provide a focus for study of structure function relationships among G proteins involved in ion channel regulation. Our work has resulted in the definition of the normal cellular physiology of epithelial ion channel modulation and the pathophysiology of the regulatory components in ion channel activity such as those seen in cystic fibrosis.

 

References:

  1. Verkman AS, Lencer WI, Brown D, and Ausiello DA. 1988. Endosomes from kidney collecting tubule cells contain the vasopressin-sensitive water channel. Nature. 333: 268-269.
  2. Stow J, D'Almedia B, Narula N, Holtzman EJ, Ercolani L, and Ausiello DA. 1991. A Heterotrimeric G Protein , G alpha i-3, on Golgi Membranes Regulates the Secretion of a Heparan Sulfate Proteoglycan in LLC-PK1 Epithelial Cells. J. Cell Biol. 114: 1113-1124.
  3. Holtzman EJ, Harris HW, Jr Kolakowski LF, Jr Goay-Woodford LM, Botelho B, Ausiello DA. 1993. A molecular defect in the vasopressin V2 - receptor gene causing nophrogenic diabetes insipidus. New Engl. J. Med. 328: 1534-37.
  4. Williams KP, Liu XH, Schumacher TNM, Lin HY, Ausiello DA, Kim PS, and Bartel  DP. 1997. Bioactive and Nuclease-Resistant L-DNA Ligand of Vasopressin. Proc. Natl. Acad. Sci. USA 94: 11285-90.