Tyrosine-based membrane protein sorting signals are differentially interpreted by polarized Madin-Darby canine kidney and LLC-PK1 epithelial cells.
Tyrosine-dependent sequence motifs are implicated in sorting membrane proteins to the basolateral domain of Madin-Darby canine kidney (MDCK) cells. We find that these motifs are interpreted differentially in various polarized epithelial cell types. The H, K-ATPase beta subunit, which contains a tyrosine-based motif in its cytoplasmic tail, was expressed in MDCK and LLC-PK1 cells. This protein was restricted to the basolateral membrane in MDCK cells, but was localized to the apical membrane in LLC-PK1 cells. Similarly, HA-Y543, a construct in which a tyrosine-based motif was introduced into the cytoplasmic tail of influenza hemagglutinin, was sorted to the basolateral membrane of MDCK cells and retained at the apical membrane of LLC-PK1 cells. A chimera in which the cytoplasmic tail of the H,K-ATPase beta subunit protein was replaced with the analogous region of the Na,K-ATPase beta subunit polypeptide was localized to both surface domains of MDCK cells. Mutation of tyrosine-20 of the H,K-ATPase beta subunit cytoplasmic sequence to an alanine was sufficient to disrupt basolateral localization of this polypeptide. In contrast, these constructs all remain localized to the apical membrane in LLC-PK1 cells. The FcRII-B2 protein bears a di-leucine motif and is found at the basolateral membrane of both MDCK and LLC-PK1 cells. These results demonstrate that polarized epithelia are able to discriminate between different classes of specifically defined membrane protein sorting signals.
Roush
D L
DL
Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut 06510, USA.
Gottardi
C J
CJ
Naim
H Y
HY
Roth
M G
MG
Caplan
M J
MJ
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D017931:DNA Primers; D004285:Dogs; D004705:Endocytosis; D004847:Epithelial Cells / Q000201:enzymology / Q000378:metabolism / Q000648:ultrastructure; D017506:H(+)-K(+)-Exchanging ATPase / Q000737:chemistry / Q000378:metabolism; D007668:Kidney / Q000201:enzymology / Q000378:metabolism / Q000648:ultrastructure; D018374:LLC-PK1 Cells; D008565:Membrane Proteins / Q000378:metabolism*; D016253:Microscopy, Immunoelectron; D008969:Molecular Sequence Data; D000254:Sodium-Potassium-Exchanging ATPase / Q000737:chemistry / Q000378:metabolism; D013552:Swine; D014443:Tyrosine / Q000378:metabolism*
D017931:DNA Primers; D008565:Membrane Proteins; D014443:Tyrosine; D017506:H(+)-K(+)-Exchanging ATPase; D000254:Sodium-Potassium-Exchanging ATPase