title: Chemical genetic screening identifies sulfonamides that raise organellar pH and interfere with membrane traffic.
abstract: Chemical genetics seeks to identify small molecules that afford functional dissection of cell biological pathways. Previous screens for small molecule inhibitors of exocytic membrane traffic yielded the identification and characterization of several compounds that block traffic from the Golgi to the cell surface as well as transport from the endoplasmic reticulum to the Golgi network [Feng et al. Proc Natl Acad Sci USA 2003;100:6469-6474; Yarrow et al. Comb Chem High Throughput Screen 2003;6:279-286; Feng et al. EMBO Reports 2004: in press]. Here, we screened these inhibitors for potential effects on endocytic membrane traffic. Two structurally related sulfonamides were found to be potent and reversible inhibitors of transferrin-mediated iron uptake. These inhibitors do not block endoplasmic reticulum-to-Golgi transport, but do disrupt Golgi-to-cell surface traffic. The compounds are members of a novel class of sulfonamides that elevate endosomal and lysosomal pH, down-regulate cell surface receptors, and impair recycling of internalized transferrin receptors to the plasma membrane. In vitro experiments revealed that the sulfonamides directly inhibit adenosine triphosphate (ATP) hydrolysis by the V-ATPase and that they also possess a potent proton ionophore activity. While maintenance of organellar pH is known to be a critical factor in both endocytosis and exocytosis, the precise role of acidification, beyond the uncoupling of ligands from their receptors, remains largely unknown. Identification of this novel class of sulfonamide inhibitors provides new chemical tools to better understand the function of organelle pH in membrane traffic and the activity of V-ATPases in particular.
authors.affiliation: Harvard Medical School, Department of Cell Biology and The CBR Institute for Biomedical Research, 200 Longwood Avenue, Boston MA, 02115, USA.
authors.forename: Thomas J F
authors.initials: TJ
authors.lastname: Nieland
authors.forename: Yan
authors.initials: Y
authors.lastname: Feng
authors.forename: Jing Xu
authors.initials: JX
authors.lastname: Brown
authors.forename: Tuan Daniel
authors.initials: TD
authors.lastname: Chuang
authors.forename: Peter D
authors.initials: PD
authors.lastname: Buckett
authors.forename: Jin
authors.initials: J
authors.lastname: Wang
authors.forename: Xiao-Song
authors.initials: XS
authors.lastname: Xie
authors.forename: Timothy E
authors.initials: TE
authors.lastname: McGraw
authors.forename: Tomas
authors.initials: T
authors.lastname: Kirchhausen
authors.forename: Marianne
authors.initials: M
authors.lastname: Wessling-Resnick
mesh_terms: D000251:Adenosine Triphosphatases / Q000737:chemistry; D000255:Adenosine Triphosphate / Q000737:chemistry; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism*; D004396:Coloring Agents / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation; D004721:Endoplasmic Reticulum / Q000378:metabolism; D011992:Endosomes / Q000378:metabolism; D004847:Epithelial Cells; D005089:Exocytosis; D005821:Genetic Techniques; D006056:Golgi Apparatus / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007476:Ionophores / Q000494:pharmacology; D007501:Iron / Q000737:chemistry / Q000378:metabolism; D020014:K562 Cells; D007700:Kinetics; D008247:Lysosomes / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000378:metabolism; D008956:Models, Chemical; D011522:Protons; D011973:Receptors, LDL / Q000096:biosynthesis; D013449:Sulfonamides / Q000737:chemistry* / Q000378:metabolism; D014168:Transferrin / Q000737:chemistry; D025262:Vacuolar Proton-Translocating ATPases / Q000378:metabolism; D014759:Viral Envelope Proteins / Q000378:metabolism; D001616:beta-Galactosidase / Q000378:metabolism
chemical_list: D004396:Coloring Agents; C028391:G protein, vesicular stomatitis virus; D007476:Ionophores; D008562:Membrane Glycoproteins; D011522:Protons; D011973:Receptors, LDL; D013449:Sulfonamides; D014168:Transferrin; D014759:Viral Envelope Proteins; D000255:Adenosine Triphosphate; D007501:Iron; D001616:beta-Galactosidase; D000251:Adenosine Triphosphatases; D025262:Vacuolar Proton-Translocating ATPases