Expression of IGF-II/Man-6-P receptors on rat, rabbit, and human colon epithelial cells.
Previous experiments from this laboratory have established the presence of receptors for insulin and insulin-like growth factor I (IGF-I) on apical membranes prepared from rabbit colon epithelial cells; however, no receptors for multiplication-stimulating activity (MSA), the rat peptide hormone equivalent of human IGF-II, were found in this tissue. In the current studies, radioligand binding assays, covalent cross-linking experiments, and immunoblot analyses using a polyclonal rabbit antiserum that recognizes the IGF-II/mannose 6-phosphate (Man-6-P) receptor, all confirmed the presence of IGF-II/Man-6-P receptors on membranes prepared from rat and human colon epithelial cells. Exposure of rat colon epithelial cell membrane fractions to 5 mM Man-6-P before incubation with 125I-labeled IGF-II increased radioligand binding. Immunoblot analysis indicated that IGF-II/Man-6-P receptors were present in both unfractionated rat colon membranes and fractions enriched with apical membranes. Rabbit and human colon epithelial cells displayed a different pattern of receptor distribution than rat colon epithelial cells, with more insulin receptors but relatively few IGF-II/Man-6-P receptors. Immunohistochemical studies using a rabbit polyclonal antiserum confirmed that IGF-II/Man-6-P receptors were present on both the apical and the basolateral surfaces of colon epithelial cells.
Pillion
D J
DJ
Metabolic Diseases Research Laboratory/Department of Pharmacology, University of Alabama, Birmingham 35294.
Grizzle
W E
WE
Yang
M
M
Meezan
E
E
Stockard
C R
CR
Ganapathy
V
V
Leibach
F H
FH
Myers
R B
RB
Haskell
J F
JF
D000818:Animals; D001345:Autoradiography; D015153:Blotting, Western; D003106:Colon / Q000166:cytology / Q000378:metabolism*; D003432:Cross-Linking Reagents; D006801:Humans; D007150:Immunohistochemistry; D007335:Insulin-Like Growth Factor II / Q000378:metabolism*; D007413:Intestinal Mucosa / Q000166:cytology / Q000378:metabolism*; D008360:Mannosephosphates / Q000378:metabolism*; D011817:Rabbits; D011869:Radioligand Assay; D051381:Rats; D017451:Receptors, Somatomedin / Q000378:metabolism*
D003432:Cross-Linking Reagents; D008360:Mannosephosphates; D017451:Receptors, Somatomedin; C027693:mannose-6-phosphate; D007335:Insulin-Like Growth Factor II