Dynamic regulation of small Rho GTPases via serotonin receptors in neurons: Effects on the cytoskeleton, neuronal morphology and functions
Final Report Abstract
Although the importance of small GTPases of the Rho family, including RhoA, Rac1 and Cdc42 in neuronal morphogenesis and motility is widely accepted, the signalling components involved in the spatiotemporal regulation of the Rho-mediated pathways are not fully characterized. We have previously shown the coupling between 5-HT4R and G13-protein leading to activation of small GTPase RhoA. We have also identified Cdc42 as a downstream effector of the 5-HT7R/G12 signalling pathway. The main goal of the proposal was thus to define molecular mechanisms involved in the dynamic regulation of small GTPases activity via serotonin receptors. Moreover, we planned to investigate the functional role of the receptor-mediated cytoskeleton reorganization for modulation of neuronal morphology, motility and synaptic plasticity. Our additional focus was on the functional role of different Cdc42 isoforms (Cdc2-palm and Cdc42-prenyl) for the morphogenic signalling in neurons. Within this proposal we demonstrated that 5-HT7R/Cdc42 signaling is involved in formation of dendritic spines and synaptogenesis in different types of neurons, including hippocampal, cortical and striatal neurons. In addition to Cdc42, we unraveled involvement of the cyclin-dependent kinase 5 (Cdk5) as down-stream effector for the 5‐HT7R‐mediated morphogenic and synaptogenic effects. Moreover, we found that morphogenic properties of 5-HT7R were preserved in other cell types, including dendritic cells, where receptor stimulation affected cellular morphology and motility through the Cdc42-mediated signaling. Searching for molecular mechanisms underlying 5-HT7R-mediated signaling in neurons, we have uncovered a novel signaling pathway involving the 5-HT7R, the main receptor for hyaluronan CD44, the matrix metalloproteinase-9 (MMP-9), and Cdc42. Activation of the 5-HT7R resulted in local stimulation of MMP-9, which modulated the activity of CD44 through the proteolytic cleavage of its extracellular domain. This led to enhanced activation of Cdc42 through 5-HT7R. One important physiological consequence of this signaling pathway was an increase in elongation of dendritic spines, leading to modulation of synaptic plasticity. Moreover, we found that the brain-specific isoform of Cdc42 undergoes palmitoylation and prenylation and demonstrated that such dual lipidation plays an important role in induction of dendritic protrusion and formation of dendritic spines in hippocampal neurons. We also made substantial efforts to improve existing and to develop novel microscopy approaches for quantitative analysis of the receptormediated signalling in living neurons. Among others, we developed an approach called “enhanced sectioned imaging property” (eSIP), which allows for precise and reproducible calibration of different microscopic systems.
Publications
- (2013) Analysis of Receptor-Receptor Interaction by Combined Application of FRET and Microscopy. In: Methods in Cell Biology. Elsevier Group. 117:243-265
Prasad S, Zeug A, Ponimaskin E
(See online at https://doi.org/10.1016/B978-0-12-408143-7.00014-1) - (2013) Dual lipidation of the brain-specific Cdc42 isoform regulates its functional properties. Biochemical Journal. 456:311-322
Wirth A, Chen-Wacker C, Wu Y-W, Gorinski N, Filippov M, Pandey G, Ponimaskin E
(See online at https://doi.org/10.1042/BJ20130788) - (2014) Cellular mechanisms of the 5-HT7 receptor-mediated signaling, Frontiers in Behavioral Neuroscience
Guseva D., Wirth A., Ponimaskin E.
(See online at https://doi.org/10.3389/fnbeh.2014.00306) - (2015) eSIP: A novel solutionbased sectioned image property approach for microscope calibration. PlosOne, 10(8):e0134980
Butzlaff M, Weigel A, Ponimaskin E, and Zeug A
(See online at https://doi.org/10.1371/journal.pone.0134980) - (2015) Serotonin receptor 5-HT7 regulates morphology and migratory properties of dendritic cells. Journal of Cell Science. 128:2866-2880
Holst K, Guseva D, Schindler S, Sixt M, Braun A, Chopra H, Pabst O, Ponimaskin E
(See online at https://doi.org/10.1242/jcs.167999) - (2016) Cleavage of Hyaluronan and CD44 Adhesion Molecule Regulate Astrocyte Morphology via Rac1 Signalling. PLoS One 10;11(5):e0155053
Konopka A, Zeug A, Skupien A, Kaza B, Mueller F, Chwedorowicz A, Ponimaskin E, Wilczynski GM, Dzwonek J
(See online at https://doi.org/10.1371/journal.pone.0155053) - (2017) How serotonin receptors regulate morphogenic signalling in neurons. Progress in Neurobiology. 151:35-56
Wirth A, Holst K, Ponimaskin E
(See online at https://doi.org/10.1016/j.pneurobio.2016.03.007) - (2017) Palmitoylation of Cdc42 promotes spines stabilization and rescues spine density deficit in a mouse model of 22q11.2 deletion syndrome. Cerebral Cortex. 27:3618-3629
Moutin E, Nikonenko I. Stefanelli T, Wirth A, Ponimaskin E, De Roo, M, Muller D
(See online at https://doi.org/10.1093/cercor/bhw183) - (2017) Serotonin 5-HT7 receptor increases the density of dendritic spines and facilitates synaptogenesis in forebrain neurons. Journal of Neurochemistry. 141(5):647-66
Speranza L, Labus J, Volpicelli F, Guseva D, Lacivita E, Leopoldo M, Bellenchi G, di Porzio U, Bijata M, Perrone-Capano C, Ponimaskin E
(See online at https://doi.org/10.1111/jnc.13962) - (2017) Synaptic remodeling depends on signaling between serotonin receptors and the extracellular matrix. Cell Reports. 19(9):1767-1782
Bijata M, Labus J, Guseva D, Stawarski M, Butzlaff M, Dzwonek J, Schneeberg J, n Böhm K, Michaluk P, Rusakov DA, Dityatev A, Wilczyński G, Wlodarczyk J, Ponimaskin E
(See online at https://doi.org/10.1016/j.celrep.2017.05.023)
