Biology subjects

Nieuwenhuis, B.

Publications and source records attributed to Nieuwenhuis, B..

4 recordsLinked to original sources

bioRxiv2024

RABGAP1 acts as a sensor to facilitate sorting and processing of amyloid precursor protein

A key hallmark of Alzheimers disease (AD) is the accumulation of extracellular amyloid-{beta} plaques in the brains of patients. Amyloid-{beta} is a 40-42 amino acid peptide produced by the proteolytic processing of amyloid precursor protein (APP) by a series of membrane-bound proteases. APP is a type-I transmembrane protein and thus its trafficking to encounter the proteases represents a rate-limiting step in the progression of AD. Although there has been a focused research effort to understand APP processing, its trafficking itinerary and machinery is incompletely understood. To address this we have performed an unbiased interaction screen for interactors of the cytosolic tail of APP. We identified previously characterised APP binders, as well as novel interactors. We have mapped the binding of APP to multiple new machineries, including RABGAP1. We have demonstrated that RAB-GAP1 partially co-localises with APP and directly interacts with a YENPTY motif in the APP cytosolic tail. Depletion or overexpression of RABGAP1 caused mistrafficking and misprocessing of endogenous APP in both human and rodent neurons. Interestingly, this effect was dependent on the GAP activity of RABGAP1, demonstrating that RABGAP1 affects the trafficking of APP by modulating the RAB activity on endosomal subdomains. This novel trafficking mechanism has implications for other NPXY cargoes and also presents a possible therapeutic avenue to explore.

cell biology↗

bioRxiv2023

Hyperactive PI3Kinase delta enables long distance regeneration of the rat corticospinal tract

Maturation of central nervous system neurons leads to loss of their intrinsic regeneration potential. In particular after injury of the adult spinal cord there is minimal regeneration of corticospinal axons, which control gait and fine movement. Previous work has shown that knockdown of PTEN to increase PIP3 levels can promote regeneration in young animals, but the effect is much less in adults probably due to low PIP3 production. Here, we have transduced sensorimotor cortex neurons with a hyperactive form of PI3K, PI3K{delta}, which increases PIP3 in mature neurons. This enables cortical neurons to regenerate corticospinal axons and improve behavioural outcomes. We used a C4 dorsal column lesion model in adult rats and injected the right motor cortex at 4 sites concurrently with a mixture AAV1-PIK3CD and AAV1-eGFP or titre matched AAV1-eGFP only. We allowed rats to survive for 6, 9, 12 or 16 weeks. Immunostaining showed 70 - 80% co-expression in cortical neurons which remained stable at both 12 and 16 weeks. We counted GFP labelled axons in 20 m spinal cord sections. In PI3KCD-treated animals many axons were seen to have regenerated around the margins of lesions, collecting into a knot of axons with the typical appearance of regeneration at the caudal end. Tracing down the cord, and excluding axons and neurites that could have come from unlesioned ventral CST, we found axons extending up to 1 cm below lesions, numbers decreasing with distance from the lesion. After 16 weeks there were circa 200 axons at the caudal end of lesions with a regeneration index of 0.2, with half this number at 12 weeks. Behavioural testing for 16 weeks revealed functional improvements in skilled paw reaching, grip strength and ladder rung walking in rats treated with PIK3CD compared to GFP only controls. In addition to behavioural testing, functional recovery of PIK3CD treated rats was confirmed with electrophysiological recordings during which we stimulated the right pyramid. Cord dorsum potentials (CDPs) above and below lesion and EMG forepaw distal flexor muscles showed greatly increased connectivity compared with GFP only controls, lesion only controls and uninjured shams. We conclude that forcing upregulation of PI3K{delta} in cortical neurons leads to robust regeneration after spinal cord injury that results in functional restoration.

neuroscience↗

bioRxiv2020

Restoring the pattern of perineuronal net sulphation corrects age-related memory loss

Memory loss is a usual consequence of ageing and aged mice show progressive deficits in memory tasks. In aged brains, perineuronal nets (PNNs), which are implicated in plasticity and memory, become inhibitory due to decreased 6-sulphation of their glycan chains (C6S). Removal of PNNs or digestion of their glycosaminoglycans rescued age-related memory loss. Premature reduction of permissive C6S by transgenic deletion of chondroitin 6-sulfotransferase led to very early memory loss. However, restoring C6S levels in aged animals by AAV delivery or transgenic expression of 6-sulfotransferase restored memory. Low C6S levels caused loss of cortical long-term potentiation, which was restored by AAV-mediated 6-sulfotransferase delivery. The study shows that loss of C6S in the aged brain leads to declining memory and cognition. Age-related memory impairment was restored by C6S replacement or other interventions targeting perineuronal nets

neuroscience↗

bioRxiv2019

PI 3-kinase delta enhances axonal PIP3 to support axon regeneration in the adult CNS

Peripheral nervous system (PNS) neurons support axon regeneration into adulthood, whereas central nervous system (CNS) neurons lose regenerative ability after development. To better understand this decline whilst aiming to improve regeneration, we focused on phosphoinositide 3-kinase (PI3K) and its product phosphatidylinositol(3,4,5)-trisphosphate (PIP3). We found that neuronal PIP3 decreases with maturity in line with regenerative competence, firstly in the cell body and subsequently in the axon. We show that adult PNS neurons utilise two catalytic subunits of PI3K for efficient regeneration: p110 and p110{delta}. Overexpressing p110 in CNS neurons had no effect, however expression of p110{delta} restored axonal PIP3 and enhanced CNS regeneration in rat and human neurons and in transgenic mice, functioning in the same way as the hyperactivating H1047R mutation of p110. Furthermore, viral delivery of p110{delta} promoted robust regeneration after optic nerve injury. These findings demonstrate a deficit of axonal PIP3 as a reason for intrinsic regeneration failure and show that native p110{delta} facilitates axon regeneration by functioning in a hyperactive fashion.

neuroscience↗