Prakash C. Supakar

Nuclear Localization of Senescence Marker Protein-30, SMP30, in Cultured Mouse Hepatocytes and Its Similarity to RNA Polymerase

Senescence marker protein-30 (SMP30), expressed mostly in the liver, protects cells against various injuries by stimulating membrane calcium-pump activity. By immunohistochemistry and western blotting, we found that SMP30 was in both the nuclei and cytoplasm of cultured mouse hepatocytes. By a homology search, we found that a domain of the SMP30 sequence 51 amino acid residues long was 60-66% similar to bacterial and yeast RNA polymerases.

Altered expression of trefoil factor 3 and cathepsin L gene in rat kidney during aging

Alterations in a wide array of physiological functions are normal consequences of aging. It is likely that, decline in cellular and physiological functions that occur during aging are the net result of age related differential gene expression and their consequent down stream effects. In this report we demonstrate that in aged kidney there is a decrease in the expression of trefoil factor 3 gene and an age-related increase in the expression of cathepsin L gene as revealed by differential display PCR (DD-PCR) and northern blot analysis. Trefoil factor 3 is mainly expressed in the alimentary canal and protects it from the degradative effect of HCl by stimulating the goblet cells to synthesize mucin. Though the exact role of trefoil factor 3 in kidney is not known, we speculate that it has a protective role in kidney. Cathepsin L is a cysteine protease which degrades connective tissue proteins like collagen, elastin and fibronectin. Increase in the expression of cathepsin L in aged kidney leading to considerable loss of organ function in old age. Down regulation of trefoil factor 3 and up regulation of cathepsin L may contribute to lack of protection and increased age related tissue damage to kidney in aging.

Alterations in expression of senescence marker protein-30 gene by 3,3′,5-triiodo-l-thyronine (T3)

Thyroid hormone (T3) is essential for normal development, differentiation, and metabolic balance of the body. A toxic dose of T3 in animals increases the basal metabolic rate and reactive oxygen species production, resulting more oxidative stress through Ca2+ influx to cytoplasm. Senescence Marker Protein-30 (SMP30) is preferentially expressed in the liver and protects cells against various injuries by enhancement of Ca2+ efflux to either extra cellular space or intraorganellar spaces through membrane Ca2+ pump activity. In this paper we report an alteration in the level of SMP30 gene expression using RT-PCR and western blot analysis in T3 treated female Wistar rats. The results indicate that there is an induction of SMP30 expression during early hours of T3 treatment and it declines in severe hyperthyroidism. Therefore, we speculate that SMP30 is regulated by T3 and might play a protective role in hyperthyroidism.

Increased phosphorylation and decreased level of IκBα during aging in rat liver

Nuclear factor kappa B (NFκB) is an evolutionary conserved transcription factor, which coordinates various metabolic processes triggered by innate and adaptive immune responses. Supakar et al. (J. Biol. Chem. 270: 837–842, 1995) had reported a 10-fold increase in DNA binding activity of NFκB in liver of old rats. In this study, we have analyzed the changes in the level of NFκB, inhibitor of NFκB (IκBα), phosphorylated-IκBα (p-IκBα) and IκB kinase (IKK) in rat liver during aging by reverse transcription polymerase chain reaction and/or western blotting. Here we demonstrate that there is an age-dependent increase in the level of p-IκBα with concomitant decrease in the level of IκBα, which may be correlated with increased inflammation, oxidative stress and higher level of activated NFκB in rat liver in old age.

Decreased Expression of the Pancreatic Secretory Trypsin Inhibitor II Gene during Aging of the Rat Liver

The genetic constitution and differential gene expression of an organism play important roles in controlling the species-specific rate of aging and the maximum life span potential. We utilized a differential-display polymerase chain reaction technique to identify the age-dependent expression of genes in the rat liver. We demonstrate in this report, for the first time, that expression of the pancreatic secretory trypsin inhibitor II (PSTI-II) gene declines drastically during aging. We confirmed this decrease by Northern blot analysis. Low PSTI-II levels in aged animals might result in a lack of protection from prematurely activated trypsin-like proteases, which would thus enhance inflammation.