Modulation of the surface proteome through multiple ubiquitylation pathways in African Trypanosomes

Recently we identified multiple suramin-sensitivity genes with a genome wide screen in Trypanosoma brucei that includes the invariant surface glycoprotein ISG75, the adaptin-1 (AP-1) complex and two deubiquitylating enzymes (DUBs) orthologous to ScUbp15/HsHAUSP1 and pVHL-interacting DUB1 (type I), designated TbUsp7 and TbVdu1, respectively. Here we have examined the roles of these genes in trafficking of ISG75, which appears key to suramin uptake. We found that, while AP-1 does not influence ISG75 abundance, knockdown of TbUsp7 or TbVdu1 leads to reduced ISG75 abundance. Silencing TbVdu1 also reduced ISG65 abundance. TbVdu1 is a component of an evolutionarily conserved ubiquitylation switch and responsible for rapid receptor modulation, suggesting similar regulation of ISGs in T. brucei. Unexpectedly, TbUsp7 knockdown also blocked endocytosis. To integrate these observations we analysed the impact of TbUsp7 and TbVdu1 knockdown on the global proteome using SILAC. For TbVdu1, ISG65 and ISG75 are the only significantly modulated proteins, but for TbUsp7 a cohort of integral membrane proteins, including the acid phosphatase MBAP1, that is required for endocytosis, and additional ISG-related proteins are down-regulated. Furthermore, we find increased expression of the ESAG6/7 transferrin receptor and ESAG5, likely resulting from decreased endocytic activity. Therefore, multiple ubiquitylation pathways, with a complex interplay with trafficking pathways, control surface proteome expression in trypanosomes

Effect of Electron Beam Irradiation on Physicochemical and Sensory characteristics of Traditional Ice cream

Introduction: Due to the increasing use of irradiation in food safety as an efficient and supplement method, it is needed to investigate effects of this new technology on the apparent and organoleptic characteristics of different products. Because primarily thing that attracts the attention of the customer to buy a food product is its appearance characteristics. The aim of this study was to determine the effect of electron beam irradiation on traditional ice cream. Methods: Ice cream samples were shopped in the city and were moved to the laboratory in defined conditions into the cool box to keep sample frozen. In keeping with freezing conditions, samples were irradiated by electron beam in -18at doses of 0, 1, 2, 3 and 5 kGy. And after one week of storage at -18℃, physicochemical tests including moisture, fat, sugar, pH and sensory tests including color, odor, taste and overall acceptability, were done on it. Results: Results showed that there was no significant difference between irradiated and non-irradiated in the amount of sugar, fat and pH. However, it can be seen significant differences in the moisture content measured in the treated samples with electron beam and untreated one (p<0.05) Also, although the doses of 1 and 2 kGy had no significant effect on the organoleptic characteristics of the product, but with increasing irradiation dose up to 2 kGy, overall acceptability&nbsp; ​​and color significantly decreased (p<0.05). Conclusion: According to the result, &nbsp;it can be concluded that the maximum recommended dose is 2 kGy for irradiation traditional ice cream product and &nbsp;higher doses caused a decline in quality of product

Streamlined Architecture and Glycosylphosphatidylinositol-dependent Trafficking in the Early Secretory Pathway of African Trypanosomes

The variant surface glycoprotein (VSG) of bloodstream form Trypanosoma brucei (Tb) is a critical virulence factor. The VSG glycosylphosphatidylinositol (GPI)-anchor strongly influences passage through the early secretory pathway. Using a dominant-negative mutation of TbSar1, we show that endoplasmic reticulum (ER) exit of secretory cargo in trypanosomes is dependent on the coat protein complex II (COPII) machinery. Trypanosomes have two orthologues each of the Sec23 and Sec24 COPII subunits, which form specific heterodimeric pairs: TbSec23.1/TbSec24.2 and TbSec23.2/TbSec24.1. RNA interference silencing of each subunit is lethal but has minimal effects on trafficking of soluble and transmembrane proteins. However, silencing of the TbSec23.2/TbSec24.1 pair selectively impairs ER exit of GPI-anchored cargo. All four subunits colocalize to one or two ER exit sites (ERES), in close alignment with the postnuclear flagellar adherence zone (FAZ), and closely juxtaposed to corresponding Golgi clusters. These ERES are nucleated on the FAZ-associated ER. The Golgi matrix protein Tb Golgi reassembly stacking protein defines a region between the ERES and Golgi, suggesting a possible structural role in the ERES:Golgi junction. Our results confirm a selective mechanism for GPI-anchored cargo loading into COPII vesicles and a remarkable degree of streamlining in the early secretory pathway. This unusual architecture probably maximizes efficiency of VSG transport and fidelity in organellar segregation during cytokinesis