Mammalian oocytes store proteins for the early embryo on cytoplasmic lattices

Mammalian oocytes are filled with poorly understood structures called cytoplasmic lattices. First discovered in the 1960s and speculated to correspond to mammalian yolk, ribosomal arrays, or intermediate filaments, their function has remained enigmatic to date. Here, we show that cytoplasmic lattices are sites where oocytes store essential proteins for early embryonic development. Using super-resolution light microscopy and cryoelectron tomography, we show that cytoplasmic lattices are composed of filaments with a high surface area, which contain PADI6 and subcortical maternal complex proteins. The lattices associate with many proteins critical for embryonic development, including proteins that control epigenetic reprogramming of the preimplantation embryo. Loss of cytoplasmic lattices by knocking out PADI6 or the subcortical maternal complex prevents the accumulation of these proteins and results in early embryonic arrest. Our work suggests that cytoplasmic lattices enrich maternally provided proteins to prevent their premature degradation and cellular activity, thereby enabling early mammalian development.

[Progress in endosomal Na⁺,K⁺/H⁺ antiporter in Arabidopsis thaliana]

Important progress has been made in the interpretation of subcellular location, ion transport characteristics and biological functions of endosomal Na⁺,K⁺/H⁺ antiporter in Arabidopsis thaliana. The endosomal Na⁺,K⁺/H⁺ antiporter contain two members, AtNHX5 and AtNHX6, whose amino acid sequence similarity is 78.7%. Studies have shown that AtNHX5 and AtNHX6 are functionally redundant, and they are all located in Golgi, trans-Golgi network (TGN), endoplasmic reticulum (ER) and prevacuolar compartment (PVC). AtNHX5 and AtNHX6 are critical for salt tolerance stress and the homeostasis of pH and K⁺. It has been reported that there are conservative acidic amino acid residues that can regulate their ion activity in the endosomal NHXs transmembrane domain, which plays a decisive role in their own functions. The results of the latest research indicate that endosomal NHXs affect vacuolar transport and protein storage, and participate in the growth of auxin-mediated development in A. thaliana. In this paper, the progress of subcellular localization, ion transport, function and application of endosomal NHXs in A. thaliana was summarized.

Stable Protein Gel Storage in Acetonitrile for Mass Spectrometric Analysis

Long-term storage of protein samples for transportation is a challenge in the field of mass spectrometric analysis because the low temperature condition is not easy to be maintained. Here we introduce a simple method to preserve proteins at room temperature for at least one month. In this method, the protein sample is run shortly into a polyacrylamide gel which is then excised after Coomassie staining. The protein gel band is then dehydrated by 100% acetonitrile three times and kept in 100% acetonitrile for storage at room temperature. By the TMT 10-plex based quantitative proteomic analyses, we have found that these proteins are stable in their levels and modifications (phosphorylation, oxidation, and ubiquitination) for 30 days. Further analysis has revealed this storage method also well preserves proteins even at 45 °C. We therefore recommend to use acetonitrile to dehydrate and store protein gel pieces as an effective alternative for sample shipping over days. Therefore, it might facilitate worldwide collaborations in the mass spectrometry-based proteomic research.