Genomic deletion of GIT2 induces a premature age-related thymic dysfunction and systemic immune system disruption

Abstract

Recent research has proposed that GIT2 (G protein-coupled receptor kinase interacting protein 2) acts as an integrator of the aging process through regulation of ‘neurometabolic’ integrity. One of the commonly accepted hallmarks of the aging process is thymic involution. At a relatively young age, 12 months old, GIT2−/− mice present a prematurely distorted thymic structure and dysfunction compared to age-matched 12 month-old wild-type control (C57BL/6) mice. Disruption of thymic structure in GIT2−/− (GIT2KO) mice was associated with a significant reduction in the expression of the cortical thymic marker, Troma-I (cytokeratin 8). Double positive (CD4+CD8+) and single positive CD4+ T cells were also markedly reduced in 12 month-old GIT2KO mice compared to age-matched control wild-type mice. Coincident with this premature thymic disruption in GIT2KO mice was the unique generation of a novel cervical ‘organ’, i.e. ‘parathymic lobes’. These novel organs did not exhibit classical peripheral lymph node-like characteristics but expressed high levels of T cell progenitors that were reflexively reduced in GIT2KO thymi. Using signaling pathway analysis of GIT2KO thymus and parathymic lobe transcriptomic data we found that the molecular signaling functions lost in the dysfunctional GIT2KO thymus were selectively reinstated in the novel parathymic lobe – suggestive of a compensatory effect for the premature thymic disruption. Broader inspection of high-dimensionality transcriptomic data from GIT2KO lymph nodes, spleen, thymus and parathymic lobes revealed a systemic alteration of multiple proteins (Dbp, Tef, Per1, Per2, Fbxl3, Ddit4, Sin3a) involved in the multidimensional control of cell cycle clock regulation, cell senescence, cellular metabolism and DNA damage. Altered cell clock regulation across both immune and non-immune tissues therefore may be responsible for the premature ‘aging’ phenotype of GIT2KO mice.

Reaction of cell membrane bilayers “as a variable capacitor” with G-protein: a reason for neurotransmitter signaling

“…These effects allow one for introducing a capacitive susceptibility that can be resonates with self-induction effect of helical coils in G proteins. Table 5 indicates the calculated helical proteins self-induction (of some G-proteins component) [63][64][65][66][67][68][69][70][71][72][73][74] through resonance with capacitances of several phospholipids membranes. Due to the greater inductance compared to conductance in coils, the helical coils of DNA, mRNA, and trance membrane proteins can be resonate with a capacitive susceptibility of phospholipids capacitors in biological phenomenon.…”

G Protein-Coupled Receptor Systems as Crucial Regulators of DNA Damage Response Processes

“…Additional investigations revealed that GIT2 interacts with many proteins involved in multiple signaling pathways linked to aging such as ATM, p53 and BRCA1. All of these proteins are involved in stress-responsive cascades and play important roles in cell cycle/DDR control, circadian clock regulation [ 157 , 210 , 211 ] and generation of SASP phenotypes in immune tissues [ 211 ]. Ectopic elevation of GIT2 expression in neuronal and non-neuronal tissues is able to attenuate the extent of DNA DSB damage induced by both ionizing radiation and chemotherapeutic DNA-damaging agents (cisplatin) [ 210 ].…”

“…Further reinforcing this permissive role of GIT2 in the aging process, it was shown that genomic deletion of GIT2 resulted in an accelerated rate of γ-H 2 AX lesion inclusion in central nervous cortex tissue in experimental mice [ 210 ]. In addition to the damage caused to brain tissues in GIT2 knockout (GIT2KO) mice, it was recently demonstrated that genomic deletion of GIT2 led to a significant co-reduction of multiple circadian clock-related mRNA transcripts in a broad range of immunological tissues including spleen, thymus and multiple lymph nodes [ 211 ]. This downregulation of GIT2 with associated clock-related proteins has been associated with premature aging (evidenced by accelerated thymic involution), the creation of a SASP-like phenotype and DDR functions [ 211 ].…”

“…In addition to the damage caused to brain tissues in GIT2 knockout (GIT2KO) mice, it was recently demonstrated that genomic deletion of GIT2 led to a significant co-reduction of multiple circadian clock-related mRNA transcripts in a broad range of immunological tissues including spleen, thymus and multiple lymph nodes [ 211 ]. This downregulation of GIT2 with associated clock-related proteins has been associated with premature aging (evidenced by accelerated thymic involution), the creation of a SASP-like phenotype and DDR functions [ 211 ]. These data together suggest that GIT2 may act as a functional connector between cellular senescence, clock regulation and DNA damage repair and as such could possess the capacity to alter the accumulation of age-related cellular damage.…”

Transcription‐Related Dynamics from Immune Disability into Endogenous Innovation

“…[1][2][3] As the cradle and educators of immature T-cells, thymus serves as dynamic role to mediate lymphopoietic activity. [8,9] Thymus recession also impairs the capacity to recover adaptive immunity following immune depletion in patients. Early thymus shares the same rudiment with parathyroid for development, [4] with original roles in enhancing reproductive system and adolescence growth, which gives obvious evidence as an erstwhile endocrine organ.…”