Biology subjects

Jojoa Cruz, S.

Publications and source records attributed to Jojoa Cruz, S..

4 recordsLinked to original sources

bioRxiv2026

De novo design of transmembrane accessory subunits for fold stabilization and expansion

Transmembrane (TM) proteins play essential roles in biology as transporters, ion channels, chaperones, enzymes, and mediators of signal transduction. However, membrane proteins often suffer from inefficient folding and intrinsic instability. Misfolding in cells can cause numerous loss-of-function pathologies. Likewise, denaturation upon purification in the laboratory is a critical barrier to structure determination and characterization of key biochemical mechanisms. Generalizable strategies to stabilize membrane proteins remain limited. Here, we developed an informatics-based de novo design strategy to create synthetic auxiliary subunits that interact with the TM helices of a model pentameric ion channel, thereby bolstering folding while maintaining channel function. Biochemical and structural characterization reveal the synthetic TM subunits can also be used to create larger multi-spanning designer proteins of custom topology. This proof-of-concept motivates the feasibility of computationally designed accessory TM helices as potential pharmacological chaperone "folding correctors" of membrane proteins in disease and as tools in structural biology.

biochemistry↗

bioRxiv2023

Structure-guided mutagenesis of OSCAs reveals differential activation to mechanical stimuli

The dimeric two-pore OSCA/TMEM63 family has recently been identified as mechanically activated ion channels. Previously, based on the unique features of the structure of OSCA1.2, we postulated the potential involvement of several structural elements in sensing membrane tension1. Interestingly, while OSCA1, 2, and 3 clades are activated by membrane stretch in cell-attached patches (i.e., they are stretch-activated channels), they differ in their ability to transduce membrane deformation induced by a blunt probe (poking). In an effort to understand the domains contributing to mechanical signal transduction, we used cryo-electron microscopy to solve the structure of Arabidopsis thaliana (At) OSCA3.1, which, unlike AtOSCA1.2, only produced stretch- but not poke-activated currents in our initial characterization2. Mutagenesis and electrophysiological assessment of conserved and divergent putative mechanosensitive features of OSCA1.2 reveal a selective disruption of the macroscopic currents elicited by poking without considerable effects on stretch-activated currents (SAC). Our results support the involvement of the amphipathic helix and lipid-interacting residues in the membrane fenestration in the response to poking. Our findings position these two structural elements as potential sources of functional diversity within the family.

biochemistry↗

bioRxiv2018

Cryo-EM structure of the mechanically activated ion channel OSCA1.2

Introduction Introduction Main Author Contributions Expression constructs Protein expression and... Cryo-EM sample preparation and... Cryo-EM image processing Model building and refinement Molecular dynamics simulations Generation of mutant, cell... Electrophysiology Methods Data availability References Methods References Mechanically activated (MA) ion channels underlie touch, hearing, shear-stress sensing, and response to turgor pressure1,2. Previously reported as putative ion channels sensitive to osmolality3-5, members of ...

biophysics↗

bioRxiv2018

OSCA/TMEM63 are an Evolutionarily Conserved Family of Mechanically Activated Ion Channels

IntroductionMechanotransduction, the conversion of mechanical cues into biochemical signals, is crucial for many biological processes in plants and animals1,2. In mammals, some mechanosensory processes such as touch sensation and vascular development are mediated by the PIEZO family of mechanically activated (MA) ion channels3-5. In plants, the impact of gravity or soil properties on root development, wind on stem growth, and turgor pressure on plant-cell size and shape are proposed to involve activation of MA ion channels6,7. Homologues of the bacterial MA channel MscS (MSLs) exist in plants, and MSL8 is shown to be involved in pollen hydration8; however, the identity of the MA channels required for most mechanotransduction processes in plants have remained elusive9. Here, we identify various members of the 15 OSCA proteins from Arabidopsis thaliana (previously reported as hyperosmolarity sensors10,11) as MA ion channels. Purification and reconstitution of OSCA1.2 in liposomes induced stretch-activated currents, suggesting that OSCAs are inherently mechanosensitive, pore-forming ion channels. This conclusion is confirmed by a high-resolution electron microscopy structure of OSCA1.2 described in a companion paper12. Beyond plants, we present evidence that fruit fly, mouse, and human TMEM63 family of proteins, homologues of OSCAs, induce MA currents when expressed in naive cells. Our results suggest that OSCA/TMEM63 proteins are the largest family of MA ion channels identified, and are conserved across eukaryotes. We anticipate that further characterization of OSCA isoforms which have diverse biophysical properties, will help gain substantial insight on the molecular mechanism of MA ion channel gating and permeation. OSCA1.1 mutant plants have impaired leaf and root growth under stress, potentially linking this ion channel to a mechanosensory role11. We expect future studies to uncover novel roles of OSCA/TMEM63 channels in mechanosensory processes across plants and animals.

biophysics↗