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.
Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut 06510, USA.
D L
DL
Roush
C J
CJ
Gottardi
H Y
HY
Naim
M G
MG
Roth
M J
MJ
Caplan
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