Targeting CK2 eliminates senescent cells and prolongs lifespan in Zmpste24-deficient mice.

Senescent cell clearance is emerging as a promising strategy for treating age-related diseases. Senolytics are small molecules that promote the clearance of senescent cells; however, senolytics are uncommon and their underlying mechanisms remain largely unknown. Here, we investigated whether genomic instability is a potential target for senolytic. We screened small-molecule kinase inhibitors involved in the DNA damage response (DDR) in Zmpste24-/- mouse embryonic fibroblasts, a progeroid model characterized with impaired DDR and DNA repair. 4,5,6,7-tetrabromo-2-azabenzamidazole (TBB), which specifically inhibits casein kinase 2 (CK2), was selected and discovered to preferentially trigger apoptosis in Zmpste24-/- cells. Mechanistically, inhibition of CK2 abolished the phosphorylation of heterochromatin protein 1α (HP1α), which retarded the dynamic HP1α dissociation from repressive histone mark H3K9me3 and its relocalization with γH2AX to DNA damage sites, suggesting that disrupting heterochromatin remodeling in the initiation of DDR accelerates apoptosis in senescent cells. Furthermore, feeding Zmpste24-deficient mice with TBB alleviated progeroid features and extended their lifespan. Our study identified TBB as a new class senolytic compound that can reduce age-related symptoms and prolong lifespan in progeroid mice.

Role of C-Terminal Phosphorylation of Lamin A in DNA Damage and Cellular Senescence.

The nuclear matrix protein lamin A is a multifunctional protein with roles in DNA replication and repair, gene activation, transcriptional regulation, and maintenance of higher-order chromatin structure. Phosphorylation is the main determinant of lamin A mobility in the nucleus and nuclear membrane dissolution during mitosis. However, little is known about the regulation of lamin A phosphorylation during interphase. Interestingly, C-terminal lamin A mutations trigger cellular senescence. Recently, we showed that the C-terminal region of lamin A interacts with casein kinase II (CK2). In the present study, we have expanded on our previous research to further investigate lamin A phosphorylation and elucidate the mechanisms underlying the effect of C-terminal mutations on cellular senescence. Our results indicate that glycogen synthase kinase 3ß (GSK3ß) and CK2 jointly mediate the phosphorylation of lamin A at C-terminal Ser628 and Ser636 residues. Furthermore, a loss of phosphorylation at either of these two sites affects the nuclear distribution of lamin A, leading to an impaired DNA damage response as well as cellular senescence. Thus, phosphorylation at C-terminal sites in lamin A appears to be important for maintaining genomic stability and preventing cellular senescence. These findings provide insight into how loss of the C-terminal region of lamin A may induce premature aging. Furthermore, enhancement of GSK3ß and CK2 activity may represent a possible therapeutic approach for the treatment of aging-related diseases.

Lamin A buffers CK2 kinase activity to modulate aging in a progeria mouse model.

Defective nuclear lamina protein lamin A is associated with premature aging. Casein kinase 2 (CK2) binds the nuclear lamina, and inhibiting CK2 activity induces cellular senescence in cancer cells. Thus, it is feasible that lamin A and CK2 may cooperate in the aging process. Nuclear CK2 localization relies on lamin A and the lamin A carboxyl terminus physically interacts with the CK2α catalytic core and inhibits its kinase activity. Loss of lamin A in Lmna-knockout mouse embryonic fibroblasts (MEFs) confers increased CK2 activity. Conversely, prelamin A that accumulates in Zmpste24-deficent MEFs exhibits a high CK2α binding affinity and concomitantly reduces CK2 kinase activity. Permidine treatment activates CK2 by releasing the interaction between lamin A and CK2, promoting DNA damage repair and ameliorating progeroid features. These data reveal a previously unidentified function for nuclear lamin A and highlight an essential role for CK2 in regulating senescence and aging.

Validated quantitation of underivatized amino acids in human blood samples by volatile ion-pair reversed-phase liquid chromatography coupled to isotope dilution tandem mass spectrometry.

Quantitation of amino acids in complex matrixes without derivatization is advantageous; however, difficulties exist in both the separation and the detection of those compounds. A validated method that is based on the use of volatile ion-pair liquid chromatography coupled to stable isotope dilution tandem mass spectrometry has been developed for the simple and accurate quantitation of underivatized amino acids in biological samples. Sufficient separation of 22 underivatized amino acids was achieved on a C18 column in 36 min using perfluoroheptanoic acid (PFHA) and trifluoroacetic acid (TFA) as mobile phase modifiers. The collisionally activated dissociation spectra of the amino acids were investigated and the transitions of [M + H]+ --> [M + H - 46]+, which are specific to alpha-amino acids, were used for the detection of most amino acids and their stable isotopes. The calibration curves were linear over the range of 0.10-100 microg/mL, and the detection limits were 0.03-20 pmol on column. The quantitative results by this method were compared with those by an established OPA-derivatization HPLC method in the assay of 8 human serum samples, and better recovery and precision data of this method were observed. The method was also applied to the neonatal screening for phenylketonuria (PKU) with dry blood spots, and the results were satisfactory. This is the first time that all proteinogenic amino acids have been quantified directly from biological extracts without any kind of derivaization. The technique shows potential for routine determination of amino acids and analogous compounds in complex matrixes.