Endocytosis of alpha 2-macroglobulin is developmentally regulated during myogenesis.
A monoclonal antibody, H143, reacts with an intracellular antigen present and accumulated in E63 rat myoblasts. H143 is directed against a species-specific determinant on purified equine serum alpha 2-macroglobulin. Immunofluorescence analyses of differentiating myoblasts grown in horse serum demonstrate that the capacity to take up alpha 2-macroglobulin is stage-specific: the rapid uptake of alpha 2-macroglobulin characteristic of myoblasts ceases prior to their fusion to form multinucleate fibers (myotubes). Neither rat fibroblasts nor a developmentally defective mutant of E63 exhibit this change in alpha 2-macroglobulin uptake. The temperature and calcium requirements for the uptake of H143 antigen, and its accumulation as effected by lysosomotropic amines, indicate that alpha 2-macroglobulin is taken up by myoblasts via a developmentally regulated endocytic process. Electron microscopy using equine alpha 2-macroglobulin labeled with colloidal gold supports this finding.
K R
KR
Haye
R F
RF
Foster
J P
JP
Goff
S J
SJ
Kaufman
D000643:Ammonium Chloride / Q000494:pharmacology; D000818:Animals; D000911:Antibodies, Monoclonal; D002118:Calcium / Q000494:pharmacology; D002478:Cells, Cultured; D002738:Chloroquine / Q000494:pharmacology; D004705:Endocytosis; D000939:Epitopes / Q000032:analysis; D005455:Fluorescent Antibody Technique; D005779:Immunodiffusion; D008854:Microscopy, Electron; D008858:Microscopy, Phase-Contrast; D024510:Muscle Development; D051381:Rats; D000511:alpha-Macroglobulins / Q000378:metabolism*
D000911:Antibodies, Monoclonal; D000939:Epitopes; D000511:alpha-Macroglobulins; D000643:Ammonium Chloride; D002738:Chloroquine; D002118:Calcium