The senescence marker protein (SMP-2) of the rat liver: purification, immunochemical characterization and age-dependent regulation.
In vitro translation of total rat hepatic mRNAs has identified a 31 kilodalton senescence marker protein (SMP-2) which is present in higher amounts in prepubertal and senescent males than in the post-pubertal adult male (more than 10-fold). SMP-2 is an androgen-repressible protein. The negative regulation of the SMP-2 gene activity by androgen accounts for its increased expression during the androgen insensitive states of the prepubertal and senescent livers, and its constitutive expression in the female liver. A combination of separation procedures including salt fractionation, chromatofocusing, ion-exchange chromatography and preparative gel electrophoresis have led to the purification of SMP-2 to apparent homogeneity. The purified protein showed the same electrophoretic mobility as the sex- and age-specific in vitro translation product of hepatic mRNAs. The polyclonal antibody to SMP-2 was produced in the rabbit. The antibody selectively reacted with the 31 kDa sex- and age-specific translation product of hepatic mRNAs. Western blot analysis of the liver cytosol confirms monospecificity of the antiserum, as well as age- and sex-dependent changes in the tissue level of SMP-2. Histochemical staining of liver sections with the antiserum reveals a preferential periportal localization of SMP-2 in the hepatocytes. This finding is in marked contrast to the androgen-inducible alpha 2u globulin which is preferentially synthesized and localized in the pericentral hepatocytes. Thus, the zonal distribution of SMP-2 correlates with polarized androgen sensitivity of the hepatocytes within the liver lobule.
Chatterjee
B
B
Department of Cellular, University of Texas Health Science Center, San Antonio 78284.
Mancini
M A
MA
Roy
A K
AK
D000375:Aging / Q000378:metabolism*; D000510:Alpha-Globulins; D000728:Androgens / Q000494:pharmacology; D000818:Animals; D000918:Antibody Specificity; D015153:Blotting, Western; D002135:Calcium-Binding Proteins; D003600:Cytosol / Q000032:analysis; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D007150:Immunohistochemistry; D008099:Liver / Q000032:analysis / Q000254:growth & development*; D008297:Male; D009693:Nucleic Acid Hybridization; D014176:Protein Biosynthesis; D011506:Proteins / Q000235:genetics / Q000302:isolation & purification*; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D011919:Rats, Inbred Strains; D012727:Sex Characteristics; D015238:Sulfotransferases
D000510:Alpha-Globulins; D000728:Androgens; D002135:Calcium-Binding Proteins; D011506:Proteins; D012333:RNA, Messenger; C013803:alpha 2u globulin; D015238:Sulfotransferases; C028152:alcohol sulfotransferase