1. Interactions between plant lipid-binding proteins and their ligands
Ze-Hua Guo, Shiu-Cheung Lung, Mohd Fadhli Hamdan, Mee-Len Chye Prog Lipid Res. 2022 Apr;86:101156.doi: 10.1016/j.plipres.2022.101156.Epub 2022 Jan 20.
Lipids participate in diverse biological functions including signal transduction, cellular membrane biogenesis and carbon storage. Following de novo biosynthesis in the plastids, fatty acids (FAs) are transported as acyl-CoA esters to the endoplasmic reticulum where glycerol-3-phosphate undergoes a series of acyl-CoA-dependent acylation via the Kennedy pathway to form triacylglycerols for subsequent assembly into oils. Alternatively, newly synthesized FAs are incorporated into phosphatidylcholine (PC) by a PC:acyl-CoA exchange process defined as "acyl editing". Acyl-CoA-binding proteins (ACBPs) at various subcellular locations can function in lipid transfer by binding and transporting acyl-CoA esters and maintaining intracellular acyl-CoA pools. Widely distributed in the plant kingdom, ACBPs are found in all eukaryotes and some eubacteria. In both rice and Arabidopsis, six forms of ACBPs co-exist and are classified into four groups based on their functional domains. Their conserved four-helix structure facilitates interaction with acyl-CoA esters. ACBPs also interact with phospholipids as well as protein partners and function in seed oil regulation, development, pathogen defense and stress responses. Besides the ACBPs, other proteins such as the lipid transfer proteins (LTPs), annexins and lipid droplet-associated proteins are also important lipid-binding proteins. While annexins bind Ca2+ and phospholipids, LTPs transport lipid molecules including FAs, acyl-CoA esters and phospholipids.
2. Mycobacterial taxonomy
T M Shinnick, R C Good Eur J Clin Microbiol Infect Dis. 1994 Nov;13(11):884-901.doi: 10.1007/BF02111489.
The minimal standards for including a species in the genus Mycobacterium are i) acid-alcohol fastness, ii) the presence of mycolic acids containing 60-90 carbon atoms which are cleaved to C22 to C26 fatty acid methyl esters by pyrolysis, and iii) a guanine + cytosine content of the DNA of 61 to 71 mol %. Currently, there are 71 recognized or proposed species of Mycobacterium which can be divided into two main groups based on growth rate. The slowly growing species require > 7 days to form visible colonies on solid media while the rapidly growing species require < 7 days. Slowly growing species are often pathogenic for humans or animals while rapidly growing species are usually considered nonpathogenic for humans, although important exceptions exist. The taxonomic and diagnostic characteristics of medically important species and of newly described species of the Mycobacterium genus are reviewed.
3. Aryl Hydrocarbon Receptor Signaling Prevents Activation of Hepatic Stellate Cells and Liver Fibrogenesis in Mice
Jiong Yan, Hung-Chun Tung, Sihan Li, Yongdong Niu, Wojciech G Garbacz, Peipei Lu, Yuhan Bi, Yanping Li, Jinhan He, Meishu Xu, Songrong Ren, Satdarshan P Monga, Robert F Schwabe, Da Yang, Wen Xie Gastroenterology. 2019 Sep;157(3):793-806.e14.doi: 10.1053/j.gastro.2019.05.066.Epub 2019 Jun 3.
Background & aims:The role of aryl hydrocarbon receptor (AhR) in liver fibrosis is controversial because loss and gain of AhR activity both lead to liver fibrosis. The goal of this study was to investigate how the expression of AhR by different liver cell types, hepatic stellate cells (HSCs) in particular, affects liver fibrosis in mice. Methods:We studied the effects of AhR on primary mouse and human HSCs, measuring their activation and stimulation of fibrogenesis using RNA-sequencing analysis. C57BL/6J mice were given the AhR agonists 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) or 2-(1'H-indole-3'-carbonyl)-thiazole-4-carboxylic acid methyl ester (ITE); were given carbon tetrachloride (CCl4); or underwent bile duct ligation. We also performed studies in mice with disruption of Ahr specifically in HSCs, hepatocytes, or Kupffer cells. Liver tissues were collected from mice and analyzed by histology, immunohistochemistry, and immunoblotting. Results:AhR was expressed at high levels in quiescent HSCs, but the expression decreased with HSC activation. Activation of HSCs from AhR-knockout mice was accelerated compared with HSCs from wild-type mice. In contrast, TCDD or ITE inhibited spontaneous and transforming growth factor β-induced activation of HSCs. Mice with disruption of Ahr in HSCs, but not hepatocytes or Kupffer cells, developed more severe fibrosis after administration of CCl4 or bile duct ligation. C57BL/6J mice given ITE did not develop CCl4-induced liver fibrosis, whereas mice without HSC AhR given ITE did develop CCl4-induced liver fibrosis. In studies of mouse and human HSCs, we found that AhR prevents transforming growth factor β-induced fibrogenesis by disrupting the interaction of Smad3 with β-catenin, which prevents the expression of genes that mediate fibrogenesis.Conclusions:In studies of human and mouse HSCs, we found that AhR prevents HSC activation and expression of genes required for liver fibrogenesis. Development of nontoxic AhR agonists or strategies to activate AhR signaling in HSCs might be developed to prevent or treat liver fibrosis.
