Expression of IGF receptors on alveolar macrophages: IGF-induced changes in InsPi formation, [Ca2+]i, and pHi.
Expression of insulin-like growth factor-I (IGF-I) receptors and insulin-like growth factor-II/mannose-6-phosphate (IGF-II/Man6P) receptors in cultured bovine alveolar macrophages (BAM) was demonstrated by competitive binding studies and crosslinking experiments. Western blotting of protein extracts from cultured BAM using an anti bovine IGF-II/Man6P receptor antiserum (#66416) confirmed the presence of IGF-II/Man6P receptors on BAM. The effects of IGFs and Man6P on generation of inositol phosphates was measured by HPLC analysis of perchloric acid extracts from myo-[3H]inositol-labelled cultured BAM. IGF-I at nanomolar concentrations and Man6P (10[-8]-10[-3] M) stimulated the accumulation of both Ins(1,4,5)P3 and Ins(1,3,4,5)P4 after 30 sec. IGF-II (up to 2.3 x 10[-8] M) had no significant effect on inositol phosphate accumulation under the same conditions. Both IGFs and Man6P induced a rise in [Ca2+]i in cultured BAM. In addition, using the fluorescent dye SNARF-1/AM we could demonstrate rapid but small IGF-II (10[-9] M) triggered acidification (0.07 pH units) of cultured BAM. Taken together, our results indicate not only the presence of both IGF-I and IGF-II/Man6P receptors on BAM, but also provide evidence of the linkage of the IGF-I receptor to the inositol phosphate system.
Geertz
R
R
University of Hamburg, Institute of Biochemistry and Food Chemistry, Department of Biochemistry and Molecular Biology, Germany.
Kiess
W
W
Kessler
U
U
Hoeflich
A
A
Tarnok
A
A
Gercken
G
G
D000818:Animals; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism*; D002417:Cattle; D002478:Cells, Cultured; D006863:Hydrogen-Ion Concentration / Q000187:drug effects; D007295:Inositol Phosphates / Q000096:biosynthesis* / Q000378:metabolism; D007334:Insulin-Like Growth Factor I / Q000378:metabolism / Q000494:pharmacology*; D007335:Insulin-Like Growth Factor II / Q000378:metabolism / Q000494:pharmacology*; D016676:Macrophages, Alveolar / Q000378:metabolism*; D008360:Mannosephosphates / Q000494:pharmacology; D017526:Receptor, IGF Type 1 / Q000096:biosynthesis*; D017527:Receptor, IGF Type 2 / Q000096:biosynthesis*
D007295:Inositol Phosphates; D008360:Mannosephosphates; D017527:Receptor, IGF Type 2; C027693:mannose-6-phosphate; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II; D017526:Receptor, IGF Type 1; D002118:Calcium