In our latest paper, we show how dimers of the p75NTR neurotrophin receptor are indipensable for p75NTR-mediated cell death in the central nervous system. The paper has just been published in the Journal of Neuroscience.
The oligomeric state and activation mechanism that enable p75 NTR to mediate these effects have recently been called into question. In this new study, we have investigated mutant mice lacking the p75NTR death domain (DD) or a highly conserved transmembrane (TM) cysteine residue (Cys 259) implicated in receptor dimerization and activation. Neuronal death induced by proneurotrophins or epileptic seizures was assessed and compared with responses in p75NTR knock-out mice and wild-type animals. Proneurotrophins induced apoptosis of cultured hippocampal and cortical neurons from wild-type mice, but mutant neurons lacking p75NTR, only the p75NTR DD, or just Cys259 were all equally resistant to proneurotrophin-induced neuronal death. Homo-FRET anisotropy experiments demonstrated that both NGF and proNGF induce conformational changes in p75 NTR that are dependent on the TM cysteine. In vivo, neuronal death induced by pilocarpine-mediated seizures was significantly reduced in the hippocampus and somatosensory, piriform, and entorhinal cortices of all three strains of p75 NTR mutant mice. Interestingly, the levels of protection observed in mice lacking the DD or only Cys 259 were identical to those of p75 NTR knock-out mice even though the Cys 259 mutant differed from the wild-type receptor in only one amino acid residue. We conclude that, both in vitro and in vivo, neuronal death induced by p75NTR requires the DD and TM Cys259, supporting the physiological relevance of DD signaling by disulfide-linked dimers of p75NTR in the CNS.
Read the full paper HERE.
UPDATE 2016-05-25: The position has been filled.
We are seeking a laboratory technician to help us with histological studies of our lines of mutant mice. The candidates should have documented expertise in histological techniques, including tissue sectioning, immunohistochemistry and microscopy. Experience in histological analysis of nervous tissue is preferred. This is a project employment for a period of up to 2 years.
Application, including CV and reference names of two latest project supervisors should be sent to Prof. Carlos Ibanez
Deadline for application is 29th April, 2016
A targeted effort to identify novel neurotrophic factors for midbrain dopaminergic neurons resulted in the isolation of GDNF (glial cell line-derived neurotrophic factor) from the supernatant of a rat glial cell line in 1993. Over two decades and 1200 papers later, the GDNF ligand family and their different receptor systems are now recognized as one of the major neurotrophic networks in the nervous system, important for the devel- opment, maintenance and function of a variety of neurons and glial cells. The many ways in which the four mem- bers of the GDNF ligand family can signal and function allow these factors to take part in the control of multiple types of processes, from neuronal survival to axon guidance and synapse formation in the developing nervous system, to synaptic function and regenerative responses in the adult. In this review, recently published in Neurobiology Of Disease, basic aspects of GDNF signaling mechanisms and receptor systems are first summarized followed by a review of current knowledge on the physiology of GDNF activities in the central nervous system, with an eye to its relevance for neurodegenerative and neuropsychiatric diseases. Read the full paper HERE.
Our latest paper describes new NMR structures of the death domain in complex with downstream interactions RhoGDI and RIP2 as well as the death domain dimer. These are the first structural insights into p75NTR signaling and reveal many surprises for the death domain superfamily. The paper is now available online at eLife.
Death domains (DDs) mediate assembly of oligomeric complexes for activation of downstream signaling pathways through incompletely understood mechanisms. We report structures of complexes formed by the DD of p75 neurotrophin receptor (p75NTR) with RhoGDI, for activation of the RhoA pathway, with caspase recruitment domain (CARD) of RIP2 kinase, for activation of the NF-kB pathway, and with itself, revealing how DD dimerization controls access of intracellular effectors to the receptor. RIP2 CARD and RhoGDI bind to p75NTR DD at partially overlapping epitopes with over 100-fold difference in affinity, revealing the mechanism by which RIP2 recruitment displaces RhoGDI upon ligand binding. The p75NTR DD forms non-covalent, low-affinity symmetric dimers in solution. The dimer interface overlaps with RIP2 CARD but not RhoGDI binding sites, supporting a model of receptor activation triggered by separation of DDs. These structures reveal how competitive protein-protein interactions orchestrate the hierarchical activation of downstream pathways in non-catalytic receptors.
The Swedish Cancer Society (Cancerfonden) has awarded a new grant to our KI group for work on ALK7, p75 and GDNF signalling and biology. Tack för förtroendet!
In our latest paper, we show that the p75 neurotrophin receptor p75NTR can signal very differently in diferent types of neurons. Using pharmacological and genetic techniques, we demonstrate that this is partly controlled by differential proteolytic cleavage of the receptor in different cell types. The new work has appeared online in the Journal of Cell Science.
Signaling by the p75 neurotrophin receptor (p75NTR) is often referred to as cell-context dependent, but neuron-type specific signaling by p75NTR has not been systematically investigated. Here, we report that p75NTR signals very differently in hippocampal neurons (HCNs) and cerebellar granule neurons (CGNs), and present evidence indicating that this is partly controlled by differential proteolytic cleavage. NGF induced caspase-3 activity and cell death in HCNs but not in CGNs, while it stimulated NFκB activity in CGNs but not in HCNs. HCNs and CGNs displayed different patterns of p75NTRproteolytic cleavage. While the p75NTR carboxy terminal fragment (CTF) was more abundant than the intracellular domain (ICD) in HCNs, CGNs exhibited fully processed ICD with very little CTF. Pharmacological or genetic blockade of p75NTR cleavage by gamma-secretase abolished NGF-induced upregulation of NFκB activity and enabled induction of CGN death, phenocopying the functional profile of HCNs. Thus, the activities of multifunctional receptors, such as p75NTR, can be tuned into narrower activity profiles by cell-type-specific differences in intracellular processes, such as proteolytic cleavage, leading to very different biological outcomes. Read the full article HERE.
Left: Annika, Sabrina, Maritina, Karima, Nuria, Favio
Right: Lilian, Christina, Diana, Patricia, Petronella, Claire
In our latest paper, we demonstrate that spatially resolved RNA-seq is ideally suited for high resolution topographical mapping of genome-wide gene expression in heterogeneous anatomical structures such as the mammalian central nervous system. The work has appeared online in Genome Biology.
Cortical interneurons originating from the medial ganglionic eminence, MGE, are among the most diverse cells within the CNS. Different pools of proliferating progenitor cells are thought to exist in the ventricular zone of the MGE, but whether the underlying subventricular and mantle regions of the MGE are spatially patterned has not yet been addressed. In this work, we combined laser-capture microdissection and multiplex RNA-sequencing to map the transcriptome of MGE cells at a spatial resolution of 50 microns. Distinct groups of progenitor cells showing different stages of interneuron maturation were identified and topographically mapped based on their genome-wide transcriptional pattern. Although proliferating potential decreased rather abruptly outside the ventricular zone, a ventro-lateral gradient of increasing migratory capacity was identified, revealing heterogeneous cell populations within this neurogenic structure. Read the full article HERE.
Favio Krapacher obtained his PhD at the Universidad Nacional de Córdoba, Argentina, in December 2013. His thesis work focused on studies of p35 transgenic mice as a model of attention deficit hyperactivity disorder, and included a series of behavioral, pharmacological and biochemical studies. Favio joins the KI team to study the role of Alk4 signaling in controlling the differentiation and migration of specific subtypes of forebrain GABAergic interneurons.
Nuria Gresa-Arribas obtained her PhD at the Universiy of Barcelona, Spain, in 2011. Her thesis examined the neurotoxic role of pro-inflammatory microglial cells and the role of C/EBPs transcription factors. She later worked as postdoctoral fellow under the direction of Dr. Josep Dalmau at the same university for studies of autoimmune neurologic diseases associated with antibodies to neuronal cell surface or synaptic proteins. Nuria will join the KI team in November to pursue studies of p75 signaling mutant mice.
Petronella Johansson trained at Kristianstad Highschool and subsequently pursued doctoral studies at the Scottish Fish Immunology Research Centre, University of Aberdeen, United Kingdom, where she obtained a PhD in 2014. Petronella joins our group to help with mouse breeding and genotyping, as well as molecular techniques and admin duties.