Evidence that a mitogen-inducible prolactin-immunoreactive protein in rat spleen lymphocytes is aldolase A.
This study characterizes several proteins in rat spleen lymphocyte lysates and conditioned medium that are recognized by antiserum to purified rat pituitary prolactin (PRL). One of these proteins, rat prolactin-immunoreactive protein (rPIP-43), has a relative molecular mass (Mr) of 43,000 and is strongly induced by mitogenic stimulation in spleen lymphocytes. A constitutively expressed protein of this size also was detected in the IM-9 human B lymphoblastoid cell line and the Nb2 rat T lymphoma cell line. The N-terminal amino acid sequence of rPIP-43 in spleen lymphocyte lysate was analysed and found to be identical with 25 residues at the N-terminus of the glycolytic enzyme aldolase A. In further experiments, the rPRL antiserum was evaluated for cross-reactivity with an aldolase A preparation and recognized a Mr 43,000 protein in rabbit muscle. Preabsorption of rPRL antiserum with rPRL was found to greatly decrease the intensity of staining of rPRL, aldolase A and rPIP-43. Preabsorption of antiserum with aldolase A had a similar, but less pronounced effect, with the aldolase A band and rPIP-43 being stained less intensely, while there was no effect on the intensity of staining of purified rPRL. Thus, data indicate that rPIP-43 is not a structural variant of PRL, but appears to be a different protein. These results have implications for the use of PRL antiserum to detect PRL in biological samples insofar as aldolase A is a ubiquitously expressed protein.
Masten
S A
SA
Department of Pharmacology and Therapeutics, University of Florida, Gainesville 32610-0267, USA.
Shiverick
K T
KT
D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D003208:Concanavalin A / Q000494:pharmacology*; D005260:Female; D005634:Fructose-Bisphosphate Aldolase / Q000276:immunology / Q000378:metabolism*; D006801:Humans; D007106:Immune Sera; D008214:Lymphocytes / Q000187:drug effects / Q000201:enzymology; D008934:Mitogens / Q000494:pharmacology*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D011388:Prolactin / Q000276:immunology*; D011817:Rabbits; D051381:Rats; D017207:Rats, Sprague-Dawley; D013154:Spleen / Q000166:cytology* / Q000201:enzymology; D014407:Tumor Cells, Cultured
D007106:Immune Sera; D008934:Mitogens; D003208:Concanavalin A; D011388:Prolactin; D005634:Fructose-Bisphosphate Aldolase