Complex formation between the postsynaptic scaffolding protein gephyrin, profilin, and Mena: a possible link to the microfilament system.
Gephyrin is an essential component of the postsynaptic cortical protein network of inhibitory synapses. Gephyrin-based scaffolds participate in the assembly as well as the dynamics of receptor clusters by connecting the cytoplasmic domains of glycine and GABA(A) receptor polypeptides to two cytoskeletal systems, microtubules and microfilaments. Although there is evidence for a physical linkage between gephyrin and microtubules, the interaction between gephyrin and microfilaments is not well understood so far. Here, we show that neuronal gephyrin interacts directly with key regulators of microfilament dynamics, profilin I and neuronal profilin IIa, and with microfilament adaptors of the mammalian enabled (Mena)/vasodilator stimulated phosphoprotein (VASP) family, including neuronal Mena. Profilin and Mena/VASP coprecipitate with gephyrin from tissue and cells, and complex formation requires the E-domain of gephyrin, not the proline-rich central domain. Consequently, gephyrin is not a ligand for the proline-binding motif of profilins, as suspected previously. Instead, it competes with G-actin and phospholipids for the same binding site on profilin. Gephyrin, profilin, and Mena/VASP colocalize at synapses of rat spinal cord and cultivated neurons and in gephyrin clusters expressed in transfected cells. Thus, Mena/VASP and profilin can contribute to the postulated linkage between receptors, gephyrin scaffolds, and the microfilament system and may regulate the microfilament-dependent receptor packing density and dynamics at inhibitory synapses.
Giesemann
Torsten
T
Cell Biology, Zoological Institute, Technical University of Braunschweig, D-38092 Braunschweig, Germany.
Schwarz
Günter
G
Nawrotzki
Ralph
R
Berhörster
Kerstin
K
Rothkegel
Martin
M
Schlüter
Kathrin
K
Schrader
Nils
N
Schindelin
Hermann
H
Mendel
Ralf R
RR
Kirsch
Joachim
J
Jockusch
Brigitte M
BM
D008841:Actin Cytoskeleton / Q000378:metabolism*; D000199:Actins / Q000378:metabolism; D000818:Animals; D001665:Binding Sites / Q000502:physiology; D001667:Binding, Competitive / Q000502:physiology; D001923:Brain Chemistry; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D015815:Cell Adhesion Molecules / Q000378:metabolism; D002478:Cells, Cultured; D003285:Contractile Proteins; D003598:Cytoskeletal Proteins; D005260:Female; D006801:Humans; D008024:Ligands; D046911:Macromolecular Substances; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008813:Mice, Inbred ICR; D008840:Microfilament Proteins / Q000235:genetics / Q000378:metabolism*; D009433:Neural Inhibition / Q000502:physiology; D009474:Neurons / Q000166:cytology / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism; D051304:Profilins; D011485:Protein Binding / Q000502:physiology; D017434:Protein Structure, Tertiary / Q000502:physiology; D051381:Rats; D013116:Spinal Cord / Q000166:cytology / Q000378:metabolism; D013569:Synapses / Q000378:metabolism*; D014162:Transfection; D000098662:Vasodilator-Stimulated Phosphoprotein
D000199:Actins; D002352:Carrier Proteins; D015815:Cell Adhesion Molecules; D003285:Contractile Proteins; D003598:Cytoskeletal Proteins; C102176:Enah protein, mouse; D008024:Ligands; D046911:Macromolecular Substances; D008565:Membrane Proteins; D008840:Microfilament Proteins; C495738:PFN1 protein, human; C495739:Pfn1 protein, mouse; C495740:Pfn1 protein, rat; D010750:Phosphoproteins; D051304:Profilins; C073441:gephyrin; D000098662:Vasodilator-Stimulated Phosphoprotein