A unique element in the cytoplasmic tail of the type II transforming growth factor-beta receptor controls basolateral delivery.
Transforming growth factor (TGF)-beta receptors stimulate diverse signaling processes that control a wide range of biological responses. In polarized epithelia, the TGFbeta type II receptor (T2R) is localized at the basolateral membranes. Sequential cytoplasmic truncations resulted in receptor missorting to apical surfaces, and they indicated an essential targeting element(s) near the receptor's C terminus. Point mutations in the full-length receptor confirmed this prediction, and a unique basolateral-targeting region was elucidated between residues 529 and 538 (LTAxxVAxxR) that was distinct, but colocalized within a clinically significant signaling domain essential for TGFbeta-dependent activation of the Smad2/3 cascade. Transfer of a terminal 84 amino-acid fragment, containing the LTAxxVAxxR element, to the apically sorted influenza hemagglutinin (HA) protein was dominant and directed basolateral HA expression. Although delivery to the basolateral surfaces was direct and independent of any detectable transient apical localization, fluorescence recovery after photobleaching demonstrated similar mobility for the wild-type receptor and a missorted mutant lacking the targeting motif. This latter finding excludes the possibility that the domain acts as a cell membrane retention signal, and it supports the hypothesis that T2R sorting occurs from an intracellular compartment.
Murphy
Stephen J
SJ
Thoracic Diseases Research Unit, Department of Biochemistry and Molecular Biology and Mayo Clinic Cancer Center, Mayo Clinic College of Medicine, Rochester, MN 55905, USA.
Shapira
Keren E
KE
Henis
Yoav I
YI
Leof
Edward B
EB
D020816:Amino Acid Motifs; D000596:Amino Acids; D000818:Animals; D019921:Biotinylation; D019556:COS Cells; D016764:Cell Polarity; D002522:Chlorocebus aethiops; D003593:Cytoplasm / Q000378:metabolism*; D004285:Dogs; D006367:HeLa Cells; D006388:Hemagglutinins / Q000737:chemistry; D006801:Humans; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry* / Q000378:metabolism*; D021382:Protein Sorting Signals; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D000077293:Receptor, Transforming Growth Factor-beta Type I; D000077294:Receptor, Transforming Growth Factor-beta Type II; D018125:Receptors, Transforming Growth Factor beta / Q000737:chemistry* / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D017384:Sequence Deletion; D015398:Signal Transduction; D013329:Structure-Activity Relationship; D014764:Viral Proteins / Q000737:chemistry
D000596:Amino Acids; D006388:Hemagglutinins; D021382:Protein Sorting Signals; D018125:Receptors, Transforming Growth Factor beta; D011993:Recombinant Fusion Proteins; D014764:Viral Proteins; D017346:Protein Serine-Threonine Kinases; D000077293:Receptor, Transforming Growth Factor-beta Type I; D000077294:Receptor, Transforming Growth Factor-beta Type II