Immunoblot studies of the IGF-related acid-labile subunit.
Insulin-like growth factors I and II (IGF-I and II) are present in serum primarily within a ternary complex consisting of IGF, IGF-binding protein-3 (IGF-3) and acid-labile subunit (ALS). Relatively little is known about ALS as compared to the other components of the complex. We report immunoblot studies of ALS using a new rabbit antiserum to human ALS1-34. The antiserum shows high specificity for ALS, labelling only the intact 82-88 kDa doublet in whole serum. Treatment with endoglycosidase-F leads to only a partial deglycosylation of ALS in whole serum, while purified ALS is reduced to M(r) approximately 58 kDa. Acidification of both whole serum and purified ALS leads to a complete loss of ALS ability to bind to cross-linked IGFBP-3:[125I]IGF-II tracer; however, immunoblot studies show no change in the apparent M(r) of the major ALS band. Immunoblot studies of human serum shows that intact ALS is decreased in growth-hormone (GH) deficiency, increases with GH treatment, is elevated in GH excess and is unchanged with IGF-I treatment. These data provide new information regarding the characteristics of ALS and demonstrate the research utility of a highly-specific antiserum for this protein.
Liu
F
F
Department of Pediatrics, Stanford University, CA 94305.
Hintz
R L
RL
Khare
A
A
Diaugustine
R P
RP
Powell
D R
DR
Lee
P D
PD
D000172:Acromegaly / Q000097:blood; D000818:Animals; D000918:Antibody Specificity; D002352:Carrier Proteins / Q000737:chemistry / Q000276:immunology / Q000378:metabolism*; D005260:Female; D006023:Glycoproteins / Q000737:chemistry / Q000276:immunology / Q000378:metabolism*; D006031:Glycosylation; D013006:Growth Hormone / Q000172:deficiency / Q000494:pharmacology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007106:Immune Sera / Q000276:immunology; D015151:Immunoblotting; D018969:Insulin-Like Growth Factor Binding Proteins; D007335:Insulin-Like Growth Factor II / Q000378:metabolism; D046911:Macromolecular Substances; D017038:Mannosyl-Glycoprotein Endo-beta-N-Acetylglucosaminidase / Q000378:metabolism; D008970:Molecular Weight; D017698:Postmenopause / Q000097:blood; D011247:Pregnancy
D002352:Carrier Proteins; D006023:Glycoproteins; D007106:Immune Sera; D018969:Insulin-Like Growth Factor Binding Proteins; D046911:Macromolecular Substances; C075944:insulin-like growth factor binding protein, acid labile subunit; D007335:Insulin-Like Growth Factor II; D013006:Growth Hormone; D017038:Mannosyl-Glycoprotein Endo-beta-N-Acetylglucosaminidase