Biology subjects

Salinas, J.

Publications and source records attributed to Salinas, J..

5 recordsLinked to original sources

bioRxiv2024

Concerted Transport and Phosphorylation of Diacylglycerol at ER-PM Contacts Sites Regulates Phospholipid Dynamics During Stress

ABSTRACTA universal response of plants to environmental stresses is the activation of plasma membrane (PM) phospholipase C (PLC) that hydrolyzes phosphatidylinositol phosphate (PIP) to produce soluble inositol phosphate (IP) and diacylglycerol (DAG). DAG produced in this way can be either phosphorylated by PM diacylglycerol kinases (DGKs) to produce the second messenger phosphatidic acid (PA) or transferred to the endoplasmic reticulum (ER) by the Synaptotagmin 1 (SYT1) protein at ER-PM Contact Sites (CS). In Arabidopsis, the clearance of DAG at the PM (avoiding deleterious accumulation) by the transfer activity of SYT is essential to maintain PM stability after stress. In this study we identify that DGK1 and DGK2 form a module with SYT1 at ER-PM CS through interaction of their C1 and C2 domains respectively. Global transcriptomic and metabolomic analyses confirms that SYT1 and DGK1/DGK2 are functionally related and lipidomic analysis supports the hypothesis that DGK1 and DGK2 function at the ER by phosphorylating DAG transferred by SYT1 from the PM. DGK1 and DGK2 show structural similarity to human DGK{varepsilon}, the DGK isoform that function at ER-PM CS in the phosphoinositide (PI) cycle. Our data indicate that components of the PI cycle are conserved between animals and plants and provide a novel mechanism leading to an increase in the efficiency of the PI cycle by channeling the transport and hydrolysis of DAG at the ER-PM CS.

plant biology↗

bioRxiv2023

Antagonistic effects of arginine methylation of LSM4 on alternative splicing during plant stress responses

Arabidopsis PROTEIN ARGININE METHYLTRANSFERASE 5 (PRMT5) post-translationally modifies RNA-binding proteins by arginine (R) methylation. The impact of this modification on the regulation of RNA processing is largely unknown. Here we use LSM4, a component of the spliceosome, as a paradigm to study the impact of R-methylation on its function in RNA processing. We identify in vivo targets of LSM4 and show that LSM4 regulates alternative splicing of a suite of them. Furthermore, LSM4 affects mRNA levels of some of the targets, showing for the first time its role in both AS and steady-state abundance. The lsm4 and prmt5 mutants show a considerable overlap of genes with altered splicing patterns, suggesting that these might be regulated by PRMT5-dependent LSM4 methylation. Wild-type LSM4 and an unmethylable version complement the lsm4-1 growth and circadian rhythms defects, suggesting that methylation is not critical for growth in normal environments. However, LSM4 methylation increases with ABA and is necessary for plants to respond properly to salt stress. In contrast, LSM4 methylation is reduced by bacterial infection, and plants expressing unmethylable LSM4 are more resistant than plants expressing wild-type LSM4. This tolerance correlates with decreased intron retention of immune-response genes upon infection, augmenting the functional isoform. Taken together, this provides the first direct evidence that R methylation adjusts LSM4 function on pre-mRNA splicing in an antagonistic manner in response to biotic and abiotic stress. HighlightPlease provide a statement that, in fewer than 30 words, highlights the novelty of the paper for the non-expert. Arginine methylation of the LSM4 spliceosome component by PROTEIN ARGININE METHYLTRANSFERASE 5 fine-tunes alternative splicing of a set of stress-related genes to antagonistically control biotic and abiotic responses in Arabidopsis.

plant biology↗

bioRxiv2023

SIV clearance from neonatal macaques following transient CCR5 depletion

SUMMARY PARAGRAPHTreatment of people with HIV (PWH) with antiretroviral therapy (ART) results in sustained suppression of viremia, but HIV persists indefinitely as integrated provirus in CD4-expressing cells. Intact persistent provirus, the "rebound competent viral reservoir" (RCVR), is the primary obstacle to achieving a cure. Most variants of HIV enter CD4+ T cells by binding to the chemokine receptor, CCR5. The RCVR has been successfully depleted only in a handful of PWH following cytotoxic chemotherapy and bone marrow transplantation from donors with a mutation in CCR5. Here we show that long-term SIV remission and apparent cure can be achieved for infant macaques via targeted depletion of potential reservoir cells that express CCR5. Neonatal rhesus macaques were infected with virulent SIVmac251, then treated with ART beginning one week after infection, followed by treatment with either a CCR5/CD3-bispecific or a CD4-specific antibody, both of which depleted target cells and increased the rate of plasma viremia decrease. Upon subsequent cessation of ART, three of seven animals treated with CCR5/CD3-bispecific antibody rebounded quickly and two rebounded 3 or 6 months later. Remarkably, the other two animals remained aviremic and efforts to detect replication-competent virus were unsuccessful. Our results show that bispecific antibody treatment can achieve meaningful SIV reservoir depletion and suggest that functional HIV cure might be achievable for recently infected individuals having a restricted reservoir.

immunology↗

bioRxiv2021

A genetic approach to dissect the role of prefoldins in Arabidopsis

The prefoldin complex (PFDc) was identified in humans as co-chaperone of the cytosolic chaperonin TRiC/CCT. It is conserved in eukaryotes and is composed of subunits PFD1 to 6. PFDc-TRiC/CCT operates folding actin and tubulins. In addition to this function, PFDs participate in a wide range of cellular processes, both in the cytoplasm and in the nucleus, and their malfunction cause developmental alterations and disease in animals, and altered growth and environmental responses in yeast and plants. Genetic analyses in yeast indicate that not all functions performed by PFDs require the participation of the canonical complex. The lack of systematic genetic analyses in higher eukaryotes makes it difficult to discern whether PFDs participate in a particular process as canonical complex or in alternative configurations, i.e. as individual subunits or in other complexes. To tackle this question, and on the premise that the canonical complex cannot be formed if one subunit is missing, we have prepared an Arabidopsis mutant deficient in the six prefoldins, and compared various growth and environmental responses with those of the individual pfd. In this way, we demonstrate that the PFDc is required to delay flowering, for seed germination, or to respond to high salt stress, whereas two or more PFDs redundantly attenuate the response to osmotic stress. A coexpression analysis of differentially expressed genes in the sextuple mutant has identified several transcription factors, such as ABI5 or PIF4, acting downstream of PFDs. Furthermore, it has made possible to assign novel roles for PFDs, for instance, in the response to warm temperature.

plant biology↗

bioRxiv2020

Synaptotagmins Maintain Diacylglycerol Homeostasis at Endoplasmic Reticulum-Plasma Membrane Contact Sites during Abiotic Stress

Endoplasmic Reticulum-Plasma Membrane contact sites (ER-PM CS) play fundamental roles in all eukaryotic cells. Arabidopsis mutants lacking the ER-PM protein tether synaptotagmin1 (SYT1) exhibit decreased plasma membrane (PM) integrity under multiple abiotic stresses such as freezing, high salt, osmotic stress and mechanical damage. Here, we show that, together with SYT1, the stress-induced SYT3 is an ER-PM tether that also functions in maintaining PM integrity. The ER-PM CS localization of SYT1 and SYT3 is dependent on PM phosphatidylinositol-4-phosphate and is regulated by abiotic stress. Lipidomic analysis revealed that cold stress increased the accumulation of diacylglycerol at the PM in a syt1/3 double mutant relative to WT while the levels of most glycerolipid species remain unchanged. Additionally, SYT1-GFP preferentially binds diacylglycerol in vivo with little affinity for polar glycerolipids. Our work uncovers a crucial SYT-dependent mechanism of stress adaptation counteracting the detrimental accumulation of diacylglycerol at the PM produced during episodes of abiotic stress.

molecular biology↗