Biology subjects

Pantoja, O.

Publications and source records attributed to Pantoja, O..

5 recordsLinked to original sources

bioRxiv2026

Cornichon receptors couple membrane adaptation to cargo selection during ER export.

Selective export of membrane proteins from the endoplasmic reticulum (ER) is fundamental for eukaryotic cell biology, yet how trafficking receptors coordinate cargo recognition with membrane adaptation and COPII recruitment remains unknown. Cornichon homolog (CNIH) proteins comprise a conserved family of trafficking receptors that mediate ER export of ion channels, G protein-coupled receptors (GPCRs), ATP-binding cassette (ABC) and solute carrier (SLC) transporters. Here, we determine cryo-electron microscopy structures of the prototypical cornichon receptor Erv14 bound to an SLC transporter in detergent and lipid nanodiscs. We show that cargo recognition is mediated by a dynamic network of interactions, in which structural lipids stabilize the receptor-cargo interface. Nanodisc structures reveal the assembly of a second Erv14 receptor that remodels the receptor-cargo interface in response to membrane architecture, thereby reducing local membrane thickness and providing direct structural evidence that cornichon receptors buffer hydrophobic mismatch during membrane protein biogenesis. Structural and trafficking analyses further show that the second receptor recruits the COPII adaptor Sec24, coupling membrane remodelling to cargo export. Together, our findings establish that cornichon receptors couple lipid-mediated membrane adaptation with cargo selection through sequential receptor assembly, linking membrane protein folding to selective COPII-mediated ER export. One sentence summaryCornichon receptors integrate membrane adaptation with cargo recognition to coordinate membrane protein quality control and selective ER export.

cell biology↗

bioRxiv2024

The chloroplast located HKT transporter plays an important role in sporophyte development in Physcomitrium patens

Cell survival depends on the maintenance of cell homeostasis that involves all the biochemical, genomic and transport processes that take place in all the organelles within an eukaryote cell. In particular, ion homeostasis is required to regulate the membrane potential and solute transport across all membranes, any alteration in these parameters will reflect in the malfunctioning of any organelle. In plant cells, sodium transporters play a central role in keeping the concentrations of this cation across all membranes under physiological conditions to prevent its toxic effects. HKT transporters are a family of membrane proteins exclusively present in plants, with some homologs being present in prokaryotes. HKT transporters have been associated to salt tolerance in plants, retrieving any leak of the cation into the xylem, or removing it from aerial parts to be transported to the roots along the phloem. This function has been assigned as most of the HKT transporters are located at the plasma membrane. Here, we report the localization of the moss HKT from Physcomitrium patens to the thylakoid membrane, and its mutation that leads to several alterations in the phenotype of the organism, together with the changes in expression of close to 1000 genes. Down regulation of photosynthesis related genes and the upregulation of glycolysis/respiration and ion transport genes help to explain the observed phenotype.

plant biology↗

bioRxiv2022

A cornichon protein controls polar localization of the PINA auxin transporter in Physcomitrium patens

Newly synthesized membrane proteins pass through the secretory pathway starting at the endoplasmic reticulum and packaged into COPII vesicles to continue to the Golgi apparatus before reaching their membrane of residence. It is known that cargo receptor proteins form part of the COPII complex and play a role in the recruitment of cargo proteins for their subsequent transport through the secretory pathway. The role of cornichon proteins is conserved from yeast to vertebrates, but it is poorly characterized in plants. To study the role of this protein in cellular traffic mechanisms in plants, the moss Physcomitrium patens has been selected since it can be studied at the single-cell level. Here, we studied the role of the two moss cornichon homologs in the secretory pathway. Mutant analyzes revealed that cornichon genes regulate different growth processes during the moss life cycle, by controlling auxin transport; with CNIH2 functioning as a specific cargo receptor for the auxin efflux carrier PINA, with the C-terminus of the receptor regulating the interaction and trafficking of PINA.

plant biology↗

bioRxiv2022

The C-terminus of the cargo receptor Erv14p affects COPII vesicle formation and cargo delivery

The endoplasmic reticulum (ER) is the start site of the secretory pathway, where newly synthesized secreted and membrane proteins are packaged into COPII vesicles through direct interaction with the COPII coat or aided by specific cargo receptors. Little is known about how post-translational modification events regulate packaging of cargo into COPII vesicles. Erv14/Cornichon belongs to a conserved family of cargo receptors required for the selection and ER export of transmembrane proteins. In this work, we show the importance of a phosphorylation consensus site (Serine-134) at the C-terminus of Erv14. Mimicking phosphorylation of S134 (S134D) prevents the incorporation of Erv14 into COPII vesicles, delays cell growth, exacerbates growth of sec mutants, modifies ER structure, and affects localization of several plasma membrane transporters. In contrast, the dephosphorylated mimic (S134A) had less deleterious effects, but still modifies ER structure and slows cell growth. Our results suggest that a possible cycle of phosphorylation and dephosphorylation is important for the correct functioning of Erv14p. Summary statementErv14 C-terminus regulates COPII formation and cargo delivery

cell biology↗

bioRxiv2022

Mesembryanthemum crystallinum plasma membrane root aquaporins are regulated via clathrin-coated vesicles in response to salt stress

The regulation of PIP-type aquaporins in the roots of plants has been identified as an important aspect in salinity tolerance. However, the molecular and cellular details underlying this process in halophytes remain unclear. Using free flow electrophoresis and label-free proteomics, we report that the increased abundance of PIPs at the plasma membrane of Mesembryanthemum crystallinum roots under salinity conditions is regulated by clathrin-coated vesicles (CCVs). To understand this regulation, we analyzed several components of the M. crystallinum CCVs complexes: clathrin light chain (McCLC) and subunits 1 and 2 of the adaptor complex (McAP1 and McAP2). Co-localization analyses revealed the association between McPIP1;4 and McAP2 and between McPIP2;1 and McAP1, observations corroborated by mbSUS assays, suggesting that aquaporin abundance at the PM is under the control of CCVs. The ability of McPIP1;4 and McPIP2;1 to form homo- and hetero-oligomers was tested and confirmed, as well as their activity as water channels. Also, we found increased phosphorylation of McPIP2;1 only at plasma membrane in response to salt stress. Our results prompt how root PIPs from halophytes are regulated through CCVs trafficking and phosphorylation, impacting their localization, transport activity and abundance under salinity conditions. One-sentence summaryAbundance of plasma membrane aquaporins in M. crystallinum roots increases in response to salinity via a clathrin-coated vesicle-dependent mechanism.

plant biology↗