Polarized apical sorting of guanylyl cyclase C is specified by a cytosolic signal.
Receptor guanylyl cyclases respond to ligand stimulation by increasing intracellular cGMP, thereby initiating a variety of cell-signaling pathways. Furthermore, these proteins are differentially localized at the apical and basolateral membranes of epithelial cells. We have identified a region of 11 amino acids in the cytosolic COOH terminus of guanylyl cyclase C (GCC) required for normal apical localization in Madin-Darby canine kidney (MDCK) cells. These amino acids share no significant sequence homology with previously identified cytosolic apical sorting determinants. However, these amino acids are highly conserved and are sufficient to confer apical polarity to the interleukin-2 receptor alpha-chain (Tac). Additionally, we find two molecular weight species of GCC in lysates prepared from MDCK cells over-expressing GCC but observe only the fully mature species on the cell surface. Using pulse-chase analysis in polarized MDCK cells, we followed the generation of this mature species over time finding it to be detectable only at the apical cell surface. These data support the hypothesis that selective apical sorting can be determined using short, cytosolic amino acid motifs and argue for the existence of apical sorting machinery comparable with the machinery identified for basolateral protein traffic.
Hodson
Caleb A
CA
Graduate Program in Cell and Molecular Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
Ambrogi
Ilana G
IG
Scott
Robert O
RO
Mohler
Peter J
PJ
Milgram
Sharon L
SL
D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D016764:Cell Polarity; D003600:Cytosol / Q000201:enzymology; D004285:Dogs; D004847:Epithelial Cells / Q000166:cytology / Q000201:enzymology*; D006162:Guanylate Cyclase / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D021382:Protein Sorting Signals; D017434:Protein Structure, Tertiary; D017461:Receptors, Atrial Natriuretic Factor / Q000378:metabolism; D000074261:Receptors, Enterotoxin; D050705:Receptors, Guanylate Cyclase-Coupled; D018000:Receptors, Peptide / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*
D021382:Protein Sorting Signals; D018000:Receptors, Peptide; D011993:Recombinant Fusion Proteins; D006162:Guanylate Cyclase; D017461:Receptors, Atrial Natriuretic Factor; D000074261:Receptors, Enterotoxin; D050705:Receptors, Guanylate Cyclase-Coupled; C091715:atrial natriuretic factor receptor A