Intracellular distribution of transglutaminase activity during rat liver regeneration

Abstract

Transglutaminase and ornithine decarboxylase activities have been assayed at intervals after partial hepatectomy in regenerating liver cells fractionated to obtain nuclear, cytoplasmic-particulate, and cytoplasmic-soluble fractions. Ornithine decarboxylase activity, localized entirely in the cytoplasmic fractions, undergoes a dramatic induction during the first 4 h after partial hepatectomy and remains elevated. This induction is very sensitive to inhibition by cycloheximide and actinomycin D, as previously reported. Transglutaminase activity is localized in both the cytoplasm and the nucleus with the highest specific activity in the nucleus. Nuclear transglutaminase activity approximately doubles in the first 2 h of liver regeneration, apparently as a result of a translocation of enzyme from the cytoplasm to the nucleus. Inhibitor studies indicate that the translocation is not dependent upon protein or RNA synthesis. In the first 2 h, actinomycin D slightly activates transglutaminase activity in the cytoplasmic-particulate and nuclear fractions. Only at 4 h after the onset of regeneration do actinomycin D and cycloheximide show some inhibition of transglutaminase activity indicating de novo synthesis at this time. A broad increase of transglutaminase activity occurs from hours 12-16 to hour 32 after partial hepatectomy in the nuclear and cytoplasmic-particulate fraction. These data suggest the existence of a function for transglutaminase in the nucleus of rat liver cells.

Calcium‐Dependent Transglutaminase of Rat Sympathetic Ganglion in Development and After Nerve Injury

“…The identity of this protein(s) is unknown yet and is currently the subject of further investigations. An early increase in polyamine-protein conjugates selectively in nuclei has been observed during liver regeneration (Remington and Russell, 1982). Our findings therefore indicate that selective alterations in pol yamhe-conjugated proteins may be among the first regulatory events that occur after axonal injury.…”

Zonal Differences in DNA Synthesis and in Transglutaminase Activity between Perivenous versus Periportal Regions of Regenerating Rat Liver

“…28) On the other hand, early studies indicated that hepatic TGase activity increased after partial hepatectomy. 29,30) The increased TGase activity in regenerating liver is not consistent with our and other's findings and is controversial, and no one has ever gave explanations for that. A potential explanation might be obtained by taking account for a zonal difference in TGase activity during regeneration of the liver.…”

Transglutaminase Activity in Rat Brain: Characterization, Distribution, and Changes with Age

“…The subcellular distri- bution of TG activity is complex. When enzyme activity is assayed in the presence of excess amounts of an exogenous "acceptor protein" (casein), a procedure that probably reveals maximum enzyme activity, the highest specific activity is observed, as in other tissues, in the cytosol (Remington and Russell, 1982), but significant levels of activity are present in the particulate fractions as well. When TG activity is assayed in the absence of exogenous substrate, the "endogenous" activity measured reflects the presence of endogenous acceptor protein substrates that are available for the enzyme.…”