Fundación Instituto Leloir

About: Fundación Instituto Leloir is a facility organization based out in Buenos Aires, Argentina. It is known for research contribution in the topics: Dentate gyrus & Neurogenesis. The organization has 702 authors who have published 1052 publications receiving 39299 citations.

Endoplasmic reticulum calcium regulates the retrotranslocation of Trypanosoma cruzi calreticulin to the cytosol.

Abstract: For most secretory pathway proteins, crossing the endoplasmic reticulum (ER) membrane is an irreversible process. However, in some cases this flow can be reversed. For instance, misfolded proteins retained in the ER are retrotranslocated to the cytosol to be degraded by the proteasome. This mechanism, known as ER associated degradation (ERAD), is exploited by several bacterial toxins to gain access to the cytosol. Interestingly, some ER resident proteins can also be detected in the cytosol or nucleus, calreticulin (CRT) being the most studied. Here we show that in Trypanosoma cruzi a minor fraction of CRT localized to the cytosol. ER calcium depletion, but not increasing cytosolic calcium, triggered the retrotranslocation of CRT in a relatively short period of time. Cytosolic CRT was subsequently degraded by the proteasome. Interestingly, the single disulfide bridge of CRT is reduced when the protein is located in the cytosol. The effect exerted by ER calcium was strictly dependent on the C-terminal domain (CRT-C), since a CRT lacking it was totally retained in the ER, whereas the localization of an unrelated protein fused to CRT-C mirrored that of endogenous CRT. This finding expands the regulatory mechanisms of protein sorting and may represent a new crossroad between diverse physiological processes.

Complex formation regulates the glycosylation of the reversibly glycosylated polypeptide

Abstract: Reversible glycosylated polypeptides (RGPs) are highly conserved plant-specific proteins, which can perform self-glycosylation. These proteins have been shown essential in plants yet its precise function remains unknown. In order to understand the function of this self-glycosylating polypeptide, it is important to establish what factors are involved in the regulation of the RGP activity. Here we show that incubation at high ionic strength produced a high self-glycosylation level and a high glycosylation reversibility of RGP from Solanum tuberosum L. In contrast, incubation at low ionic strength led to a low level of glycosylation and a low glycosylation reversibility of RGP. The incubation at low ionic strength favored the formation of high molecular weight RGP-containing forms, whereas incubation at high ionic strength produced active RGP with a molecular weight similar to the one expected for the monomer. Our data also showed that glycosylation of RGP, in its monomeric form, was highly reversible, whereas, a low reversibility of the protein glycosylation was observed when RGP was part of high molecular weight structures. In addition, glycosylation of RGP increased the occurrence of non-monomeric RGP-containing forms, suggesting that glycosylation may favor multimer formation. Finally, our results indicated that RGP from Arabidopsis thaliana and Pisum sativum are associated to golgi membranes, as part of protein complexes. A model for the regulation of the RGP activity and its binding to golgi membranes based on the glycosylation of the protein is proposed where the sugars linked to oligomeric form of RGP in the golgi may be transferred to acceptors involved in polysaccharide biosynthesis.