RESUMEN
The membrane-bound AAA protease FtsH is the key player controlling protein quality in bacteria. Two single-pass membrane proteins, HflK and HflC, interact with FtsH to modulate its proteolytic activity. Here, we present structure of the entire FtsH-HflKC complex, comprising 12 copies of both HflK and HflC, all of which interact reciprocally to form a cage, as well as four FtsH hexamers with periplasmic domains and transmembrane helices enclosed inside the cage and cytoplasmic domains situated at the base of the cage. FtsH K61/D62/S63 in the ß2-ß3 loop in the periplasmic domain directly interact with HflK, contributing to complex formation. Pull-down and in vivo enzymatic activity assays validate the importance of the interacting interface for FtsH-HflKC complex formation. Structural comparison with the substrate-bound human m-AAA protease AFG3L2 offers implications for the HflKC cage in modulating substrate access to FtsH. Together, our findings provide a better understanding of FtsH-type AAA protease holoenzyme assembly and regulation.
Asunto(s)
Proteínas de Escherichia coli , Proteasas ATP-Dependientes/metabolismo , ATPasas Asociadas con Actividades Celulares Diversas/metabolismo , Proteínas Bacterianas/metabolismo , Microscopía por Crioelectrón , Escherichia coli/metabolismo , Proteínas de Escherichia coli/metabolismo , HumanosRESUMEN
Traumatic brain injury (TBI) remains one of the leading causes of death and disability worldwide. Mild TBI may lead to neuropsychiatric sequelae, including memory loss and motor impairment. Mitochondrial dysfunction and oxidative stress have a contributory role in several neurological disorders; however, their association with mitophagy in mild TBI is unclear. TBI was induced in female Sprague Dawley (SD) rats using a New York University Impactor (10 g, impactor head 2.5 mm diameter, weight drop 50 mm) and compared to sham surgery controls. The novel object recognition and error ladder tests were performed at 24 hours and for 6 weeks post injury, and the brains were examined histologically to confirm the extent of injury. Mitochondria manganese superoxide dismutase (MnSOD) and the oxidative phosphorylation (OXPHOS) complexes I-V (CI-CV), as well as mitophagy markers, dynamin related protein 1 (DRP-1), LC3A/B and PTEN-induced putative kinase 1 (PINK-1), were measured in the penumbra by western blot. At 24 hours sham rats performed as expected on a novel object recognition test while TBI rats showed cognitive deficits at the early time points. TBI rats also showed more early motor deficits on a horizontal ladder, compared with the sham rats. MnSOD, OXPHOS CI, CIII and CV protein levels were significantly lower in the TBI group at 24 hours. DRP-1, LC3A/B I and II, and PINK-1 were increased at 6 weeks suggesting abnormal mitophagy. Moderate TBI caused immediate cognitive and mild motor functional deficits in the rats that did not persist. Reduced antioxidative capacity and possibly compromised mitochondrial function may affect the long term functional recovery.