A comprehensive small interfering RNA screen identifies signaling pathways required for gephyrin clustering.
The postsynaptic scaffold protein gephyrin is clustered at inhibitory synapses and serves for the stabilization of GABA(A) receptors. Here, a comprehensive kinome-wide siRNA screen in a human HeLa cell-based model for gephyrin clustering was used to identify candidate protein kinases implicated in the stabilization of gephyrin clusters. As a result, 12 hits were identified including FGFR1 (FGF receptor 1), TrkB, and TrkC as well as components of the MAPK and mammalian target of rapamycin (mTOR) pathways. For confirmation, the impact of these hits on gephyrin clustering was analyzed in rat primary hippocampal neurons. We found that brain-derived neurotrophic factor (BDNF) acts on gephyrin clustering through MAPK signaling, and this process may be controlled by the MAPK signaling antagonist sprouty2. BDNF signaling through phosphatidylinositol 3-kinase (PI3K)-Akt also activates mTOR and represses GSK3β, which was previously shown to reduce gephyrin clustering. Gephyrin is associated with inactive mTOR and becomes released upon BDNF-dependent mTOR activation. In primary neurons, a reduction in the number of gephyrin clusters due to manipulation of the BDNF-mTOR signaling is associated with reduced GABA(A) receptor clustering, suggesting functional impairment of GABA signaling. Accordingly, application of the mTOR antagonist rapamycin leads to disinhibition of neuronal networks as measured on microelectrode arrays. In conclusion, we provide evidence that BDNF regulates gephyrin clustering via MAPK as well as PI3K-Akt-mTOR signaling.
Department of Molecular Biology, Naturwissenschaftliches und Medizinisches Institut an der Universität Tübingen, 72770 Reutlingen, Germany.
Jennifer
J
Wuchter
Simone
S
Beuter
Fridolin
F
Treindl
Thoralf
T
Herrmann
Günther
G
Zeck
Markus F
MF
Templin
Hansjürgen
H
Volkmer
D000818:Animals; D002352:Carrier Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D055785:Gene Knockdown Techniques / Q000379:methods; D005820:Genetic Testing / Q000379:methods*; D006367:HeLa Cells; D006801:Humans; D008565:Membrane Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D005810:Multigene Family / Q000502:physiology*; D061251:Primary Cell Culture; D034741:RNA, Small Interfering / Q000096:biosynthesis* / Q000235:genetics; D051381:Rats; D015398:Signal Transduction / Q000235:genetics*; D005680:gamma-Aminobutyric Acid / Q000502:physiology
D002352:Carrier Proteins; D008565:Membrane Proteins; D034741:RNA, Small Interfering; C073441:gephyrin; D005680:gamma-Aminobutyric Acid