Anti-biofilm potential of human senescence marker protein 30 against Mycobacterium smegmatis

Human senescence marker protein 30 (huSMP30) has been characterized as a multifaceted protein consisting of various enzymatic and cellular functions. It catalyzes the interconversion of L-gulonate and L-gulono-γ-lactone in the ascorbate biosynthesis pathway. Therefore, we hypothesized that it could be a potential anti-biofilm agent against pathogenic bacteria due to its lactonase activity. In order to corroborate this, the huSMP30 was recombinantly expressed, purified, and analyzed for its ability to inhibit Mycobacterium smegmatis biofilm formation, which showed a concentration-dependent inhibition as compared to the untreated control group. Further, in silico analysis was performed to redesign the huSMP30 with enhanced lactonase activity. Molecular docking analysis of the huSMP30 and lactone substrates facilitated the selection of three single amino acid substitutions (E18H, N154Q, and D204V), which were created using a PCR-based site-directed mutagenesis reaction. These mutant proteins and the wild-type huSMP30 were purified, and the effects on the enzymatic activity and biofilm formation were studied. The mutants E18H and D204V showed non-significant effects on specific lactonase activity, catalytic efficiency, and anti-biofilm property; however, the mutant N154Q showed significant improvement in the specific lactonase activity, catalytic efficiency, and inhibition in the biofilm formation. The protein stability analysis revealed that the wild-type huSMP30 and its designed mutants were stable at 37 °C for up to 4 days. In conclusion, the anti-biofilm property of the huSMP30 has been established, and an engineered version, N154Q, inhibits biofilm formation with greater efficiency. Human SMP30 is a versatile protein with multiple cellular and enzymatic functions, however, its anti-biofilm potential has not been explored. Our work presents the method to produce soluble and active huSMP30 in the E. coli expression system and establishes its role as an anti-biofilm agent against Mycobacterium smegmatis owing to its lactonase activity. Our results provide support for the future advancement of huSMP30 as a potential anti-biofilm agent targeting pathogenic Mycobacterium species.

Senescence marker protein30 protects lens epithelial cells against oxidative damage by restoring mitochondrial function

Etiology and pathogenesis of age-related cataract is not entirely clear till now. Senescence marker protein 30 (SMP30) is a newly discovered anti-aging factor, which plays an important role in preventing apoptosis and reducing oxidative stress damage. Mitochondria are located at the intersection of key cellular pathways, such as energy substrate metabolism, reactive oxygen species (ROS) production and apoptosis. Oxidative stress induced by 4-hydroxynonenal (4-HNE) is closely related to neurodegenerative diseases and aging. Our study focused on the effect of SMP30 on mitochondrial homeostasis of human lens epithelial cells (HLECs) induced by 4-HNE. Western blots and qPCR were used to compare the expression of SMP30 protein in the residual lens epithelial cells in the lens capsule of age-related cataract (ARC) patients and the donated transparent lens capsule. On this basis, SMP30 overexpression plasmid and SMP30 shRNA interference plasmid were introduced to explore the effect of SMP30 on the biological behavior in HLECs under the condition of oxidative stress induced by 4-HNE through immunohistochemistry, ROS evaluation, metabolic spectrum analysis and JC-1 fluorescence measurement. Given that Nuclear Factor erythroid 2-Related Factor 2 (Nrf2)/Kelch Like ECH Associated Protein 1 (KEAP1) signaling pathway is the most important antioxidant stress pathway, we further analyzed the regulatory effect of SMP30 by WB to explore its molecular mechanism. Our study indicated that SMP30 may inhibit ROS accumulation, restore mitochondrial function, activate Nrf2/Keap1 signaling pathway, therefore protecting lens epithelial cells from oxidative stress-induced cell damage.