Carboxyl Terminal Modulator Protein Induces Cell Senescence and Is Upregulated With Aging by Zic2 in Rats

Carboxyl terminal modulator protein (CTMP) may be involved in various physiological and pathological processes, such as inflammation, tumor growth, and cardiac hypertrophy. Our recent study has shown that CTMP is increased with aging and plays a role in determining brain ischemic tolerance. However, it is not known how CTMP expression with aging is regulated and whether the changed CTMP expression has an effect on cell senescence. Here, cells that stably overexpressed CTMP were generated and cell senescence biomarkers were determined. The brains of Fischer 344 male rats were harvested for Western blot analysis and immunostaining to detect CTMP and the Zinc finger protein Zic2. The regulations of CTMP expression by Zic2 were examined by promoter activity assays. Increasing CTMP enhanced cells expressing senescence-associated β-galactosidase staining but without expression of Ki67, decreased cell proliferation and colony formation, and increased cells with condensed DNA of more than one pair of homologous chromosomes caused by senescence. Zic2 was decreased with aging in rats. Zic2 and CTMP were mainly expressed in the neurons in rats. Similarly, CTMP protein was expressed in the neurons of human brain. An anti-Zic2 antibody immunoprecipitated DNA fragments of ctmp gene. Zic2 inhibited the activity of presumptive ctmp promoter. Overexpressing Zic2 decreased CTMP in cells. These results suggest that CTMP induces cell senescence and that Zic2 is a suppressor of CTMP expression. The decrease of Zic2 contributes to CTMP increase with aging.