title: Cleavage of Hyaluronan and CD44 Adhesion Molecule Regulate Astrocyte Morphology via Rac1 Signalling.
abstract: Communication of cells with their extracellular environment is crucial to fulfill their function in physiological and pathophysiological conditions. The literature data provide evidence that such a communication is also important in case of astrocytes. Mechanisms that contribute to the interaction between astrocytes and extracellular matrix (ECM) proteins are still poorly understood. Hyaluronan is the main component of ECM in the brain, where its major receptor protein CD44 is expressed by a subset of astrocytes. Considering the fact that functions of astrocytes are tightly coupled with changes in their morphology (e.g.: glutamate clearance in the synaptic cleft, migration, astrogliosis), we investigated the influence of hyaluronan cleavage by hyaluronidase, knockdown of CD44 by specific shRNA and CD44 overexpression on astrocyte morphology. Our results show that hyaluronidase treatment, as well as knockdown of CD44, in astrocytes result in a "stellate"-like morphology, whereas overexpression of CD44 causes an increase in cell body size and changes the shape of astrocytes into flattened cells. Moreover, as a dynamic reorganization of the actin cytoskeleton is supposed to be responsible for morphological changes of cells, and this reorganization is controlled by small GTPases of the Rho family, we hypothesized that GTPase Rac1 acts as a downstream effector for hyaluronan and CD44 in astrocytes. We used FRET-based biosensor and a dominant negative mutant of Rac1 to investigate the involvement of Rac1 activity in hyaluronidase- and CD44-dependent morphological changes of astrocytes. Both, hyaluronidase treatment and knockdown of CD44, enhances Rac1 activity while overexpression of CD44 reduces the activity state in astrocytes. Furthermore, morphological changes were blocked by specific inhibition of Rac1 activity. These findings indicate for the first time that regulation of Rac1 activity is responsible for hyaluronidase and CD44-driven morphological changes of astrocytes.
authors.affiliation: Laboratory of Molecular and Systemic Neuromorphology, The Nencki Institute of Experimental Biology, 02-093, Warsaw, ul. Pasteura 3, Poland.
authors.forename: Anna
authors.initials: A
authors.lastname: Konopka
authors.affiliation: Cellular Neurophysiology, Center of Physiology, Hannover Medical School, 30625, Hannover, Germany.
authors.forename: Andre
authors.initials: A
authors.lastname: Zeug
authors.affiliation: Laboratory of Molecular and Systemic Neuromorphology, The Nencki Institute of Experimental Biology, 02-093, Warsaw, ul. Pasteura 3, Poland.
authors.forename: Anna
authors.initials: A
authors.lastname: Skupien
authors.affiliation: Laboratory of Molecular Neurobiology, Neurobiology Center, The Nencki Institute of Experimental Biology, 02-093, Warsaw, ul. Pasteura 3, Poland.
authors.forename: Beata
authors.initials: B
authors.lastname: Kaza
authors.affiliation: Cellular Neurophysiology, Center of Physiology, Hannover Medical School, 30625, Hannover, Germany.
authors.forename: Franziska
authors.initials: F
authors.lastname: Mueller
authors.affiliation: Laboratory of Molecular and Systemic Neuromorphology, The Nencki Institute of Experimental Biology, 02-093, Warsaw, ul. Pasteura 3, Poland.
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Chwedorowicz
authors.affiliation: Cellular Neurophysiology, Center of Physiology, Hannover Medical School, 30625, Hannover, Germany.
authors.forename: Evgeni
authors.initials: E
authors.lastname: Ponimaskin
authors.affiliation: Laboratory of Molecular and Systemic Neuromorphology, The Nencki Institute of Experimental Biology, 02-093, Warsaw, ul. Pasteura 3, Poland.
authors.forename: Grzegorz M
authors.initials: GM
authors.lastname: Wilczynski
authors.affiliation: Laboratory of Molecular and Systemic Neuromorphology, The Nencki Institute of Experimental Biology, 02-093, Warsaw, ul. Pasteura 3, Poland.
authors.forename: Joanna
authors.initials: J
authors.lastname: Dzwonek
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001253:Astrocytes / Q000166:cytology / Q000378:metabolism*; D001921:Brain / Q000166:cytology / Q000378:metabolism*; D002448:Cell Adhesion; D002465:Cell Movement; D003599:Cytoskeleton / Q000737:chemistry / Q000378:metabolism; D005109:Extracellular Matrix / Q000737:chemistry / Q000378:metabolism*; D031541:Fluorescence Resonance Energy Transfer; D005786:Gene Expression Regulation; D018960:Hyaluronan Receptors / Q000235:genetics* / Q000378:metabolism; D006820:Hyaluronic Acid / Q000737:chemistry* / Q000378:metabolism; D006821:Hyaluronoglucosaminidase / Q000737:chemistry; D006868:Hydrolysis; D009479:Neuropeptides / Q000235:genetics* / Q000378:metabolism; D061251:Primary Cell Culture; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction; D020830:rac1 GTP-Binding Protein / Q000235:genetics* / Q000378:metabolism
chemical_list: C476399:Cd44 protein, mouse; D018960:Hyaluronan Receptors; D009479:Neuropeptides; D034741:RNA, Small Interfering; C484602:Rac1 protein, mouse; D006820:Hyaluronic Acid; D006821:Hyaluronoglucosaminidase; D020830:rac1 GTP-Binding Protein