Biology subjects

Gekara, N. O.

Publications and source records attributed to Gekara, N. O..

3 recordsLinked to original sources

bioRxiv2026

Aging-associated endo-lysosomal dysfunction drives inflammaging and neurodegeneration through the STING-IFN-I axis

All animals age. However, aging is a heterogeneous process and individual organisms age differently. Moreover, within the same organism, cells or organs do not age at the same time or speed. For instance, although neurodegeneration is a key trait of aging, neurological symptoms normally manifest long after multiple indicators of aging in peripheral tissues. The genetic determinants of aging remain poorly understood. Mutations in leucine-rich repeat kinase 2 (LRRK2) are major genetic risk factors for Parkinsons disease (PD). By analyzing PD patients and mice with LRRK2 gain of function mutation (LRRK2GoF), we demonstrate that PD is an accelerated aging disease characterized by systemic low-grade STING-dependent inflammation (inflammaging) that first manifests in the periphery then disrupts the blood brain barrier and progresses to the brain resulting in neurodegeneration. Mechanistically, we demonstrate that a primary consequence of aging or Lrrk2GoF is endolysosomal decline. This results in the cytosolic build-up of extraneous self-DNA and subsequent shedding of DNA-containing extracellular vesicles thereby triggering the cGAS- STING pathway cell-intrinsically and intercellularly in distant host cells. This study unveils the cGAS-STING pathway and LRRK2GoF as key determinants and potential targets for preventive or therapeutic strategies against accelerated aging, inflammaging and neurodegeneration.

immunology↗

bioRxiv2026

K27-linked ubiquitination restrains the NOD2-RIP2 signaling pathway

Nucleotide-binding oligomerization domain 2 (NOD2) signaling is a critical arm of host defense and immune homeostasis but requires strict regulation to prevent self-injury. Central to this regulation is the polyubiquitination of the adaptor protein RIP2, yet the precise ubiquitin linkages and their dynamic control remain incompletely understood. Here, we identify K27-linked polyubiquitination of RIP2 by the E3 ligase XIAP as a novel inhibitory signal that attenuates RIP2 complex assembly and downstream NF-{kappa}B activation, thereby fine-tuning NOD2-induced inflammatory signaling. We show that XIAP-mediated K63-linked ubiquitination promotes NOD2-RIP2 activation, whereas K27-linked ubiquitination impairs the recruitment of TAK1 and NEMO to the NOD2-RIP2 complex, dampening downstream signaling and cytokine production. We further demonstrate that this regulation is counterbalanced by the deubiquitinase MYSM1, which selectively removes K27-, K63-. and M1-polyubiquitin chains via its SWIRM-MPN domains to restore balanced signaling. Together, these findings define a dynamic XIAP-RIP2-MYSM1 axis in which opposing ubiquitin linkages fine-tune NOD2 responses, establishing a molecular rheostat for immune signaling with implications for inflammatory disease pathogenesis and opportunities for targeted therapeutic intervention.

immunology↗

bioRxiv2018

The innate immune DNA sensor cGAS is a negative regulator of DNA repair hence promotes genome instability and cell death

Stringent regulation of DNA repair is essential for organismal integrity, but the mechanisms are not fully understood. Cyclic cGMP-AMP synthase (cGAS), the DNA sensor that alerts the innate immune system to the presence of foreign or damaged self-DNA in the cytoplasm is critical for the outcome of infections, inflammatory diseases and cancer. Besides this cytoplasmic function as an innate immune sensor, whether cGAS fulfills other biological roles remains unknown. Here we report that cGAS has a distinct role in the nucleus: it inhibits homologous recombination DNA repair (HR) thereby promoting genome instability and associated micronuclear generation and mitotic death. We show that cGAS-mediated inhibition of HR requires its DNA binding and oligomerization but not its catalytic activity or the downstream innate immune signaling events. Mechanistically, we show that cGAS impede RAD51-mediated DNA strand invasion, a key step in HR. These results uncover a new function of cGAS relevant for understanding its involvement in genome instability- associated disorders.

cell biology↗