Synaptopodin, a molecule involved in the formation of the dendritic spine apparatus, is a dual actin/alpha-actinin binding protein.
Synaptopodin (SYNPO) is a cytoskeletal protein that is preferentially located in mature dendritic spines, where it accumulates in the spine neck and closely associates with the spine apparatus. Formation of the spine apparatus critically depends on SYNPO. To further determine its molecular action, we screened for cellular binding partners. Using the yeast two-hybrid system and biochemical assays, SYNPO was found to associate with both F-actin and alpha-actinin. Ectopic expression of SYNPO in neuronal and non-neuronal cells induced actin aggregates, thus confirming a cytoplasmic interaction with the actin cytoskeleton. Whereas F-actin association is mediated by a central SYNPO motif, binding to alpha-actinin requires the C-terminal domain. Notably, the alpha-actinin binding domain is also essential for dendritic targeting and postsynaptic accumulation of SYNPO in primary neurons. Taken together, our data suggest that dendritic spine accumulation of SYNPO critically depends on its interaction with postsynaptic alpha-actinin and that SYNPO may regulate spine morphology, motility and function via its distinct modes of association with the actin cytoskeleton.
Kremerskothen
Joachim
J
Department for Experimental Tumorbiology, University of Muenster, Badestrasse 9, D-48149 Muenster, Germany. kremers@uni-muenster.de
Plaas
Christian
C
Kindler
Stefan
S
Frotscher
Michael
M
Barnekow
Angelika
A
D000185:Actinin / Q000378:metabolism*; D000199:Actins / Q000378:metabolism*; D020816:Amino Acid Motifs / Q000235:genetics; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites / Q000235:genetics / Q000502:physiology; D002478:Cells, Cultured; D049229:Dendritic Spines / Q000378:metabolism*; D000882:Haplorhini; D006801:Humans; D051379:Mice; D008840:Microfilament Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D011485:Protein Binding / Q000502:physiology; D017434:Protein Structure, Tertiary / Q000235:genetics / Q000502:physiology; D051381:Rats; D017386:Sequence Homology, Amino Acid; D014162:Transfection; D020798:Two-Hybrid System Techniques
D000199:Actins; D008840:Microfilament Proteins; C503967:SYNPO protein, human; C503968:Synpo protein, mouse; C503969:Synpo protein, rat; D000185:Actinin