Secretion of antithrombin is converted from nonpolarized to apical by exchanging its amino terminus for that of apically secreted family members.
The three members of the serpin family, corticosteroid binding globulin, alpha1-antitrypsin, and C1 inhibitor are secreted apically from Madin-Darby canine kidney (MDCK) cells, whereas two homologous family members, antithrombin and plasminogen activator inhibitor-1, are secreted in a nonpolarized fashion. cDNAs coding for chimeras composed of complementary portions of an apically targeted serpin and a nonsorted serpin were generated, expressed in MDCK cells, and the ratio between apical and basolateral secretion was analyzed. These experiments identified an amino-terminal sequence of corticosteroid binding globulin (residues 1-19) that is sufficient to direct a chimera with antithrombin mainly to the apical side. A deletion/mutagenesis analysis showed that no individual amino acid is absolutely required for the apical targeting ability of amino acids 1-30 of corticosteroid binding globulin. The corresponding amino-terminal sequences of alpha1-antitrypsin and C1 inhibitor were also sufficient to confer apical sorting. Based on our results we suggest that the apical targeting ability is encoded in the conformation of the protein.
Vogel
Lotte K
LK
Department of Medical Biochemistry and Genetics, Biochemistry Laboratory C, University of Copenhagen, The Panum Institute, Blegdamsvej 3, DK-2200 Copenhagen N, Denmark. Vogel@imbg.ku.dk
Sahkri
Sia
S
Sjostrom
Hans
H
Noren
Ove
O
Spiess
Martin
M
D000595:Amino Acid Sequence; D000818:Animals; D000991:Antithrombins / Q000737:chemistry* / Q000378:metabolism*; D004247:DNA / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D004285:Dogs; D017353:Gene Deletion; D008969:Molecular Sequence Data; D009154:Mutation; D011233:Precipitin Tests; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
D000991:Antithrombins; D018076:DNA, Complementary; D011993:Recombinant Fusion Proteins; D004247:DNA