Biology subjects

Lu, Y.-B.

Publications and source records attributed to Lu, Y.-B..

4 recordsLinked to original sources

bioRxiv2026

The circ_0074371/miR-4738-3p/AMPK Signaling Axis Induces M1 Macrophage Polarization and Restricts Intracellular Survival of Mycobacterium tuberculosis

Tuberculosis, an infectious disease caused by Mycobacterium tuberculosis, remains endemic in regions where it is prevalent. Mycobacterium tuberculosis is an intracellular pathogen that can survive within host macrophages; however, the mechanisms governing its long-term persistence and the progression to active pulmonary tuberculosis remain poorly understood. Circular RNAs (circRNAs) have been implicated in the initiation and progression of numerous diseases. In our previous study, circRNA sequencing identified several circRNAs associated with tuberculosis progression. In the present study, sequencing and reverse transcription-polymerase chain reaction (RT-PCR) analyses revealed that Circ_0074371 was significantly downregulated in monocytes from patients with active pulmonary tuberculosis (ATB) and was closely associated with disease onset and progression, exhibiting considerable diagnostic value for ATB. Functional experiments further showed that Circ_0074371 significantly impaired the intracellular survival of Mtb and promoted M1 macrophage polarization. Mechanistically, Circ_0074371 acted as a competing endogenous RNA by sequestering miR-4738-3p, a potent negative regulator of AMP-activated protein kinase (AMPK) activation. Collectively, these findings identify Circ_0074371 as a tuberculosis-associated circRNA that regulates AMPK activity and reveal a novel mechanism through which Circ_0074371 influences macrophage polarization via the AMPK pathway, providing new insights into potential therapeutic targets for ATB.

immunology↗

bioRxiv2024

Elevated Ubiquitin Phosphorylation by PINK1 Contributes to Proteasomal Impairment and Promotes Neurodegeneration

Ubiquitin (Ub), a central regulator of protein turnover, can be phosphorylated by PINK1 (PTEN-induced putative kinase 1) to generate S65-phosphorylated ubiquitin (pUb). Elevated pUb levels have been observed in aged human brains and in Parkinsons disease, but the mechanistic link between pUb elevation and neurodegeneration remains unclear. Here, we demonstrate that pUb elevation is a common feature under neurodegenerative conditions, including Alzheimers disease, aging, and ischemic injury. We show that impaired proteasomal activity leads to the accumulation of sPINK1, the cytosolic form of PINK1 that is normally proteasome-degraded rapidly. This accumulation increases ubiquitin phosphorylation, which then inhibits ubiquitin-dependent proteasomal activity by interfering with both ubiquitin chain elongation and proteasome-substrate interactions. Specific expression of sPINK1 in mouse hippocampal neurons induced progressive pUb accumulation, accompanied by protein aggregation, proteostasis disruption, neuronal injury, neuroinflammation, and cognitive decline. Conversely, pink1 knockout mitigated protein aggregation in both mouse brains and HEK293 cells. Furthermore, the detrimental effects of sPINK1 could be counteracted by co-expressing Ub/S65A phospho-null mutant but exacerbated by over-expressing Ub/S65E phospho-mimic mutant. Together, these findings reveal that pUb elevation, triggered by reduced proteasomal activity, inhibits proteasomal activity and forms a feedforward loop that drives progressive neurodegeneration.

biochemistry↗

bioRxiv2023

Ubiquitin phosphorylation accelerates protein aggregation and promotes neurodegeneration in the aging brain

Ser65-phosphorylated ubiquitin (pUb) was found elevated in neurons of aged and neurodegenerative brains. Yet little is known whether a causative link exists between pUb level and brain aging. Here we show that the knockout of pink1, a Ub kinase, abolished pUb elevation and decelerated protein aggregation in aged mouse brains and cells with proteasomal inhibition. Conversely, over-expression of PINK1 but not the kinase-dead version increased the pUb level and accelerated protein aggregation by suppressing of proteasomal degradation. Furthermore, PINK1 over-expression in mouse hippocampus neurons increased pUb level and protein aggregation, slowly leading to mitochondrial injury, neurodegeneration, and cognitive impairment. Notably, the neuronal damages induced by PINK1 were rescued by the dominant negative Ub/S65A mutant, while Ub/S65E phosphomimetic mutant caused neuronal death. Together, an incidental increase of Ub phosphorylation can progressively and cumulatively cause the decline of Ub-dependent proteasomal activity, consequenting promotes neurodegeneration in the aging brain.

cell biology↗

bioRxiv2019

A key interfacial residue identified with in-cell structure characterization of a Class-A GPCR dimer

G protein coupled receptors (GPCRs) have been shown homo-dimeric. Despite extensive studies, no single residue has been found essential for dimerization. Lacking an efficient method to shift the monomer-dimer equilibrium also makes functional relevance of GPCR dimer elusive. Here, using fluorescence lifetime-based imaging for distance measurements, we characterize the dimeric structure of GPR17, a class A GPCR, in cells. The structure reveals transmembrane helices 5 and 6 the dimer interface, and pinpoints F229 a key residue, mutations of which can render GPR17 monomeric or dimeric. Using the resulting mutants, we show that GPR17 dimer is coupled to both Gi and Gq signaling and is internalized, whereas GPR17 monomer is coupled to Gi signaling only and is not internalized. We further show that residues equivalent to F229 of GPR17 in several other class A GPCRs are also important for dimerization. Our findings thus provide fresh insights into GPCR structure and function.

biochemistry↗