Small molecule agonist of mitochondrial fusion repairs mitochondrial dysfunction.

Membrane dynamics are important to the integrity and function of mitochondria. Defective mitochondrial fusion underlies the pathogenesis of multiple diseases. The ability to target fusion highlights the potential to fight life-threatening conditions. Here we report a small molecule agonist, S89, that specifically promotes mitochondrial fusion by targeting endogenous MFN1. S89 interacts directly with a loop region in the helix bundle 2 domain of MFN1 to stimulate GTP hydrolysis and vesicle fusion. GTP loading or competition by S89 dislodges the loop from the GTPase domain and unlocks the molecule. S89 restores mitochondrial and cellular defects caused by mitochondrial DNA mutations, oxidative stress inducer paraquat, ferroptosis inducer RSL3 or CMT2A-causing mutations by boosting endogenous MFN1. Strikingly, S89 effectively eliminates ischemia/reperfusion (I/R)-induced mitochondrial damage and protects mouse heart from I/R injury. These results reveal the priming mechanism for MFNs and provide a therapeutic strategy for mitochondrial diseases when additional mitochondrial fusion is beneficial.

Correction to "Carboxymethyl Chitosan Oligosaccharide Holds Promise for Treatment of Stenosis Crohn's Disease".

[This corrects the article DOI: 10.1021/acsptsci.2c00035.].

Carboxymethyl Chitosan Oligosaccharide Holds Promise for Treatment of Stenosis Crohn's Disease.

Crohn's disease (CD) is a chronic intestinal disturbance mediated by mucosal immune hyperactivity that is often associated with the formation of stenosis. No reliable solution to stenosis CD exists so far. Therefore, we generated carboxymethyl chitosan oligosaccharide (CMCOS) as a new promising therapy and investigate its efficacy in an improved rat CD model. CMCOS was synthesized by enzymatic hydrolysis, and its biosafety was evaluated in vivo. The rat model of stenosis CD was optimized by an orthogonal experiment of 75 or 100 mg/kg trinitrobenzenesulfonic acid (TNBS) in a 50 or 75% ethanol enema. The therapeutic efficacy of CMCOS on the rat model of stenosis CD was investigated and compared with the commercial drug 5-aminosalicylic acid over a 28 day period of disease progression. The rat model of stenosis CD was well established by intracolonic administration of 75 mg/kg TNBS in 75% ethanol. CMCOS significantly alleviated CD symptoms morphologically, hematologically, and pathologically, promoting functional recovery of intestinal epithelium in a dose-dependent manner. CMCOS reduced infiltrations of inflammatory cells by regulating the IL-17A/PPAR-γ pathway and reduced fibro-proliferation and fibro-degeneration of the colon tissue by downregulating the TGF-ß1/WT1 pathway. 75 mg/kg TNBS in a 75% ethanol enema induces a rat model of stenosis CD suitable for preclinical pathology and pharmacological studies. The safety, antifibrosis, and functional repair performance of CMCOS make it a promising candidate for the treatment of stenosis CD.

Transient Expression of Chimeric Fluorescent Reporter Proteins in Pollen Tubes to Study Protein Polar Secretion and Dynamics.

Transient expression of chimeric fluorescent reporter proteins by biolistic bombardment is a quick and useful procedure for studying subcellular protein localization and dynamics in plants. It is especially beneficial in specific plant cells which are not suitable for protoplast-based and Agrobacterium-mediated protein transient expression. Polar protein secretion and vesicular trafficking play essential functions for cell polarization and tip growth. The growing pollen tube is regarded as an ideal model plant cell system to study the machinery and regulation of polar protein trafficking and targeting. A large amount of newly synthesized proteins are packed and polarly transported to the apical region to support the rapid and highly polarized tip growth. Here, we described a detailed step-by-step protocol for the transient expression of chimeric fluorescent reporter proteins in growing Arabidopsis and tobacco pollen tubes to study polar transportation logistics and mechanisms. In addition, we have optimized the Arabidopsis and tobacco in vitro pollen germination medium and the conditions to maximize the efficiency of protein expression. As a proof of concept, we have used this protocol to express actin microfilament and late endosomal fluorescent markers in Arabidopsis and tobacco pollen tubes.