Developmental expression and molecular cloning of REMP, a novel retinal epithelial membrane protein.
The retinal pigment epithelium (RPE), like other transport epithelia, has a polarized distribution of membrane and cytoskeletal proteins. The establishment of a polarized phenotype is an essential step in the differentiation of the RPE and the development and maintenance of visual function. Using a monoclonal antibody (MAb 3C4) we have identified a novel membrane protein that is uniquely expressed in chick RPE. We have referred to this protein as REMP for retinal epithelial membrane protein. In these studies we characterized the expression and distribution of this protein during embryonic development and determined its primary structure by cDNA cloning. The developmental expression of REMP was examined by immunocytochemical localization. REMP was first detected in the chick RPE at Embryonic Day 5 (E5) in both apical and basolateral membranes. By E14 the distribution of REMP was restricted to the basolateral surface of the RPE cells. Biochemical fractionation and surface labeling of RPE cells suggested that REMP was an integral protein. The gene encoding REMP was isolated from an E15 chick RPE cDNA library, cloned into lambda gt11, and screened with MAb 3C4. The cDNA was sequenced and found to contain one 1350-bp open reading frame encoding for a 450-amino-acid protein. The deduced amino-acid sequence of REMP shares 32.9% identity with MCT1, a monocarboxylate transporter (Garcia, Goldstein, Pathak, Anderson, and Brown, Cell, 76, 865-873, 1994). By Northern blot analysis, REMP mRNA was detected only in RPE cells. There was an increase in the expression REMP transcript during development but when RPE cells were grown in primary culture the expression of REMP was turned off. The unique expression of REMP in the RPE in vivo would suggest a role for this protein in development and maintenance of normal retinal function.
Philp
N
N
Pennsylvania College of Optometry, Philadelphia 19141-3399, USA.
Chu
P
P
Pan
T C
TC
Zhang
R Z
RZ
Chu
M L
ML
Stark
K
K
Boettiger
D
D
Yoon
H
H
Kieber-Emmons
T
T
D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal; D030161:Avian Proteins; D001483:Base Sequence; D015153:Blotting, Western; D002352:Carrier Proteins / Q000737:chemistry; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D002642:Chick Embryo; D002522:Chlorocebus aethiops; D003001:Cloning, Molecular; D018076:DNA, Complementary; D004591:Electrophoresis, Polyacrylamide Gel; D005314:Embryonic and Fetal Development; D005136:Eye Proteins; D005786:Gene Expression Regulation; D015723:Gene Library; D007150:Immunohistochemistry; D008565:Membrane Proteins / Q000032:analysis / Q000096:biosynthesis* / Q000737:chemistry; D026901:Membrane Transport Proteins; D008969:Molecular Sequence Data; D027501:Monocarboxylic Acid Transporters; D010455:Peptides / Q000138:chemical synthesis / Q000276:immunology; D010857:Pigment Epithelium of Eye / Q000378:metabolism*; D011994:Recombinant Proteins / Q000032:analysis / Q000096:biosynthesis; D015183:Restriction Mapping; D012160:Retina / Q000196:embryology* / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D014162:Transfection
D000911:Antibodies, Monoclonal; D030161:Avian Proteins; D002352:Carrier Proteins; D018076:DNA, Complementary; D005136:Eye Proteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D027501:Monocarboxylic Acid Transporters; D010455:Peptides; C094885:REMP protein, chicken; D011994:Recombinant Proteins; C077949:Mev protein, Cricetulus griseus