Biology subjects

Palacio, S.

Publications and source records attributed to Palacio, S..

4 recordsLinked to original sources

bioRxiv2023

FAM122A ensures cell cycle interphase progression and checkpoint control as a SLiM-dependent substrate-competitive inhibitor to the B55/PP2A phosphatase

The Ser/Thr protein phosphatase 2A (PP2A) is a highly conserved collection of heterotrimeric holoenzymes responsible for the dephosphorylation of many regulated phosphoproteins. Substrate recognition and the integration of regulatory cues are mediated by B regulatory subunits that are complexed to the catalytic subunit (C) by a scaffold protein (A). PP2A/B55 substrate recruitment was thought to be mediated by charge-charge interactions between the surface of B55 and its substrates. Challenging this view, we recently discovered a conserved SLiM [RK]-V-x-x-[VI]-R in a range of proteins, including substrates such as the retinoblastoma-related protein p107 and TAU (Fowle et al. eLife 2021;10:e63181). Here we report the identification of this SLiM in FAM122A, an inhibitor of B55/PP2A. This conserved SLiM is necessary for FAM122A binding to B55 in vitro and in cells. Computational structure prediction with AlphaFold2 predicts an interaction consistent with the mutational and biochemical data and supports a mechanism whereby FAM122A uses the SLiM in the form of a short -helix to dock to the B55 top groove. In this model, FAM122A spatially constrains substrate access by occluding the catalytic subunit with a second -helix immediately adjacent to helix 1. Consistently, FAM122A functions as a competitive inhibitor as it prevents binding of substrates in in vitro competition assays and the dephosphorylation of CDK substrates by B55/PP2A in cell lysates. Ablation of FAM122A in human cell lines reduces the rate of proliferation, progression through cell cycle transitions and abrogates G1/S and intra-S phase cell cycle checkpoints. FAM122A-KO in HEK293 cells results in attenuation of CHK1 and CHK2 activation in response to replication stress. Overall, these data strongly suggest that FAM122A is a SLiM-dependent, substrate-competitive inhibitor of B55/PP2A that suppresses multiple functions of B55 in the DNA damage response and in timely progression through the cell cycle interphase.

molecular biology↗

bioRxiv2021

Do soil features condition seed germination of gypsum plants? An analysis of the effect of different natural soils

Gypseous soils are widespread across arid and semiarid environments worldwide. They present remarkable challenges to plants and host a unique flora. We aimed to assess up to what point the specificity and distribution of species on gypsum might be driven by species-specific germination responses to soil gypsum availability. We analyzed the germination of six gypsum specialists and four closely related generalist plant species from the Iberian Peninsula and the Chihuahuan Desert in four different field soils with contrasting concentrations of gypsum, pH and soil texture. Plant restriction to gypsum was unrelated to the germinating ability of seeds on different substrates. Irrespective of their affinity for gypsum, most species germinated better on mixed gypsum-calcareous soil and worse in the acidic soil treatment. Our data suggest soil pH was the main soil feature driving seed germination, while the effect of gypsum content was generally not significant. The main exception was the Iberian gypsum specialist Helianthemum squamatum (L.) Dum. Cours., which showed increased germination on gypseous soils and higher germination in response to increased soil gypsum content. Except for this species, our findings indicate alkaline soils favor the germination of most of the species analyzed, irrespectively of their gypsum content. HighlightsO_LIGypsum soils are one of the most widespread special substrates of the world C_LIO_LIWe evaluated the effects of natural soils on the germination of gypsum plants C_LIO_LISoil pH was the main soil feature driving seed germination C_LIO_LIThe effect of gypsum content was not significant C_LIO_LIWe suggest a potential origin of gypsophiles from plants adapted to alkaline soils C_LI

ecology↗

bioRxiv2019

A toolbox of nanobodies developed and validated for diverse neuroscience research applications

Nanobodies (nAbs) are small, minimal antibodies that have distinct attributes that make them uniquely suited for certain biomedical research, diagnostic and therapeutic applications. Prominent uses include as intracellular antibodies or intrabodies to bind and deliver cargo to specific proteins and/or subcellular sites within cells, and as nanoscale immunolabels for enhanced tissue penetration and improved spatial imaging resolution. Here, we report the generation and validation of nAbs against a set of proteins prominently expressed at specific subcellular sites in brain neurons. We describe a novel hierarchical validation pipeline to systematically evaluate nAbs isolated by phage display for effective and specific use as intrabodies and immunolabels in mammalian cells including brain neurons. These nAbs form part of a robust toolbox for targeting proteins with distinct and highly spatially-restricted subcellular localization in mammalian brain neurons, allowing for visualization and/or modulation of structure and function at those sites.

neuroscience↗

bioRxiv2018

Organizing neuronal ER-PM junctions is a conserved nonconducting function of Kv2 plasma membrane ion channels

Endoplasmic reticulum (ER) and plasma membrane (PM) form junctions crucial to ion and lipid signaling and homeostasis. The Kv2.1 ion channel is unique among PM proteins in organizing ER-PM junctions. Here, we show that this organizing function is conserved between Kv2 family members that differ in their biophysical properties, modulation and cellular expression. Manipulation of actin cytoskeleton surrounding Kv2 ER-PM junctions affects their spatial organization. Kv2-containing ER-PM junctions overlap with those formed by canonical ER-PM tethers. ER-PM junction organization by Kv2 channels is unchanged by point mutations that eliminate ion conduction, but abolished by those that eliminate PM clustering without impacting ion channel function. Kv2.2 is distinct in lacking the reversible modulation of junction organization present in Kv2.1. Brain neurons in Kv2 double knockout mice have altered ER-PM junctions, demonstrating a conserved in vivo function for Kv2 family members distinct from their canonical role as ion-conducting channels shaping neuronal excitability.

cell biology↗