Biology subjects

Parra-Rivas, L. A.

Publications and source records attributed to Parra-Rivas, L. A..

4 recordsLinked to original sources

bioRxiv2024

Long term rescue of Alzheimer deficits in vivo by one-time gene-editing of App C-terminus.

Gene-editing technologies promise to create a new class of therapeutics that can achieve permanent correction with a single intervention. Besides eliminating mutant alleles in familial disease, gene-editing can manipulate upstream pathophysiologic events and alter disease-course in wider patient populations. Here we use CRISPR-Cas9 to edit the last exon of amyloid precursor protein (App), relevant for Alzheimers disease (AD). Our strategy effectively eliminates an endocytic (YENPTY) motif at APP C-terminus in mouse and human neurons, while preserving N-terminus and compensatory APP-homologues. This manipulation favorably alters events along the amyloid-pathway; inhibiting toxic APP-beta-cleavage fragments (including Abeta) and upregulating neuroprotective APP-alpha-cleavage. AAV-editing ameliorates neuropathologic, electrophysiologic, and behavioral deficits in an AD knockin mouse model. Effects persist for many months with no detectable abnormalities in germline-edited WT mice, and pathologic alterations in glial-transcriptomes are also normalized. Our strategy takes advantage of innate transcriptional rules that render terminal exons insensitive to nonsense-decay, and this upstream manipulation is expected to be effective for all forms of AD.

neuroscience↗

bioRxiv2023

Synapsin E-domain is essential for α-synuclein function

The cytosolic proteins synucleins and synapsins are thought to play cooperative roles in regulating synaptic vesicle (SV) recycling, but mechanistic insight is lacking. Here we identify the synapsin E-domain as an essential functional binding-partner of -synuclein (-syn). Synapsin E-domain allows -syn functionality, binds to -syn, and is necessary and sufficient for enabling effects of -syn at the synapse. Together with previous studies implicating the E-domain in clustering SVs, our experiments advocate a cooperative role for these two proteins in maintaining physiologic SV clusters.

neuroscience↗

bioRxiv2022

Serine-129 phosphorylation of α-synuclein is a trigger for physiologic protein-protein interactions and synaptic function

Phosphorylation of -synuclein at the Serine-129 site (-syn Ser129P) is an established pathologic hallmark of synucleinopathies, and also a therapeutic target. In physiologic states, only a small fraction of total -syn is phosphorylated at this site, and consequently, almost all studies to date have focused on putative pathologic roles of this post-translational modification. We noticed that unlike native (total) -syn that is widely expressed throughout the brain, the overall pattern of -syn Ser129P is restricted, suggesting intrinsic regulation and putative physiologic roles. Surprisingly, preventing phosphorylation at the Ser-129 site blocked the ability of -syn to attenuate activity-dependent synaptic vesicle (SV) recycling - widely thought to reflect its normal function. Exploring mechanisms, we found that neuronal activity augments -syn Ser-129P, and this phosphorylation is required for -syn binding to VAMP2 and synapsin - two functional binding-partners that are necessary for -syn function. AlphaFold2-driven modeling suggests a scenario where Ser129P induces conformational changes in the C-terminus that stabilizes this region and facilitates protein-protein interactions. Our experiments indicate that the pathology-associated Ser129P is an unexpected physiologic trigger of -syn function, which has broad implications for pathophysiology and drug-development.

neuroscience↗

bioRxiv2022

Syntaxin Habc is required to open Unc18 to template SNARE assembly

SNARE and Unc18 proteins form the core of the membrane fusion complex at synapses. The fusion machinery is evolutionarily ancient and mediates constitutive fusion in yeast. We demonstrate that the SNARE and Unc18 machinery in the nematode C. elegans can be replaced by yeast proteins and still carry out synaptic transmission. However, substitutions of individual components from yeast disrupts fusion. To understand the functional interactions within the core machinery we adopted an interspecies complementation approach using yeast. Synaptic transmission could be restored in chimeras when two key interfaces were present: a novel Habc-Unc18 contact site and an Unc18-SNARE motif contact site. An open form of Unc18 could bypass the requirement for the Habc-Unc18 interface. Together, these data suggest that the Habc domain of syntaxin is required for Unc18 to adopt an open conformation; open Unc18 then templates SNARE complex formation.

neuroscience↗