The DNA repair protein ku is involved in gp130-mediated signal transduction events in PBMC from young but not from elderly subjects

Proteodynamics in aging human T cells - The need for its comprehensive study to understand the fine regulation of T lymphocyte functions

Cellular life depends mostly on the creation, modification, interactions and destruction of proteins. This is true for every cell, including human T lymphocytes. One way these cells can ascertain the fidelity and at least partial functionality of their proteomes under constant attack of irreversible modulations (e.g., ROS- or glycation-dependent) is proteostasis. However, with cellular aging proteostasis progressively fails and proteostenosis (decreased amounts and functionalities of remaining proteins) occurs. There are several mechanisms involved in the modulation and protection of the proteome in the T cells which include mainly multiple layers of vesicle-bound and cytoplasmic proteases (e.g., lysosomal and proteasomal ones) acting mostly by degradation of obsolete and age-modified proteins. Recently it was shown that another not yet so widely known system consisting of obligatorily calcium-dependent cysteine proteases, the calpains and their inhibitor, the calpastatin serves in T cells as a dual switch, either activating or inactivating different proteins depending on intracellular conditions. Thus the proteolytic elimination of altered proteins as well as modulation of activity of those remaining leads to dynamic change of proteome composition and function (proteodynamics) in aging lymphocytes, so far in an almost unknown way. Aging T cell proteodynamics requires further comprehensive analysis of the resulting lysoproteomic patterns and their changes.

The role of immunity in elderly cancer

The increased incidence of malignancies in elderly patients living in industrialized countries has led to both identify the causes that alter the normal homeostatic balance in elderly and designate the specific treatments. The progressive decline of the immune system (immunosenescence) involving cellular and molecular alterations impact both innate and adaptive immunity. The immunosenescence leads to increased incidence of infectious diseases morbidity and mortality as well as heightened rates of other immune disorders such as autoimmunity, cancer, and inflammatory conditions. Here, we summarize the knowledge on the major changes in the immune system associated with aging in primary lymphoid organs as well as a description of molecular mechanisms, and the impact on cancer development.

Age-related transcription levels of KU70, MGST1 and BIK in CD34+ hematopoietic stem and progenitor cells

Despite the known longevity of human hematopoietic stem and progenitor cells (HSC), numerous functional impairments of these cells can be observed in an age-dependent manner. However, the molecular alterations associated with aging of HSC are largely unknown. Therefore, we scrutinized gene expression patterns of HSC from newborn, young and old healthy donors. CD34+ HSC were isolated via immuno-magnetic separation and evaluated by FACS analysis. We performed cDNA macroarray analyses on a first set of CD34+ samples (n=13). We found the genes encoding KU-antigen 70 kD (KU70), microsomal glutathione S-transferase 1 (MGST1) and BCL2-interacting killer (BIK) to possess age-related mRNA expression levels. KU70 is a DNA repair gene and part of the DNA-dependent protein kinase (DNA-PK) complex. Its expression was negatively correlated with donor age showing highest expression levels in newborn, 2.6-fold lower levels in young and 6.3-fold lower levels in old donors. The transcription levels of MGST1, a gene protecting against oxidative stress, progressively increased with age. Expression was lowest in newborn, 2.6-fold higher in young and 4.3-fold higher in old donors. BIK is a proapoptotic gene and its expression was positively correlated with donor age: lowest in newborn, 1.8-fold higher in young and 4.1-fold higher in old donors. These findings were confirmed with an independent, second set of CD34+ samples (n=16) by means of quantitative real-time RT-PCR. Elucidation of age-dependent molecular alterations in healthy HSC facilitate a better understanding of functional impairments in hematopoiesis and may become valuable for anti-aging drug development and the emerging field of regenerative medicine.

A deficiency in Drak2 results in a T cell hypersensitivity and an unexpected resistance to autoimmunity

DRAK2 is a member of the death-associated protein (DAP)-like family of serine/threonine kinases. Members of this family induce apoptosis in various cell types. DRAK2, in particular, is specifically expressed in T cells and B cells, and it is differentially regulated during T cell development. To determine whether DRAK2 regulates lymphocyte apoptosis, we produced Drak2(-/-) mice. Contrary to our expectations, Drak2(-/-) T cells did not demonstrate any defects in apoptosis or negative selection; however, T cells from Drak2(-/-) mice exhibited enhanced sensitivity to T cell receptor-mediated stimulation with a reduced requirement for costimulation. These results provide evidence that DRAK2 raises the threshold for T cell activation by negatively regulating signals through the TCR. In contrast to other models of T cell hypersensitivity, Drak2(-/-) mice were remarkably resistant to experimental autoimmune encephalomyelitis (EAE). These results expose a new pathway regulating T cell activation and highlight the intricacies of induced autoimmune disease.