Dynamin 3 Is a Component of the Postsynapse, Where it Interacts with mGluR5 and Homer

Abstract

The dynamins comprise a large family of mechanoenzymes known to participate in membrane modeling events. All three conventional dynamin genes (Dyn1, Dyn2, Dyn3) are expressed in mammalian brain and produce more than 27 different dynamin proteins as a result of alternative splicing. Past studies have suggested that Dyn1 participates in specialized neuronal functions such as rapid synaptic vesicle recycling, while Dyn2 may mediate the conventional clathrin-mediated uptake of surface receptors. Currently, the distribution, expression, and function of Dyn3 in neurons, or in any other cell type, are completely undefined. Here, we demonstrate that Dyn1 and Dyn3 localize differentially in the synapse. Dyn1 concentrates within the presynaptic compartment, while Dyn3 localizes to dendritic spine tips. Within the postsynaptic density (PSD), we found Dyn3, but not Dyn1, to be part of a biochemically isolated complex comprised of Homer and metabotropic glutamate receptors. Finally, although dominant-negative Dyn3 did not seem to inhibit receptor endocytosis, overexpression of a specific Dyn3 spliced variant in mature neurons caused a marked remodeling of dendritic spines. These data suggest that Dyn3 is a postsynaptic dynamin and, like its binding partner Homer, plays a significant role in dendritic spine morphogenesis and remodeling.

Alsin Is a Rab5 and Rac1 Guanine Nucleotide Exchange Factor

“…Cell Culture, Transfections, and Infections-Hippocampal neuron cultures from E18 Sprague-Dawley rats were prepared and maintained as described previously (37). NIH3T3 cells and SH-SY5Y cells were maintained in a 37°C, 5% CO 2 environment and cultured in Dulbecco's modified Eagle's medium (Invitrogen) and Dulbecco's modified Eagle's/ F-12 (1:1) media (HyClone Laboratories, Logan, UT), respectively, supplemented with fetal bovine serum (10%), penicillin (100 units/ml), and streptomycin (100 g/ml).…”

“…Immunofluorescence-Hippocampal neurons were processed for immunofluorescence as described previously (37). Primary antibodies were incubated at dilutions of 1:50 (alsin) and 1:250 (MAP2b) and secondary antibodies (Alexa488 anti-rabbit and Alexa568 anti-mouse) at 1:1000.…”

Homer/Vesl Proteins and Their Roles in CNS Neurons

“…After the original proposal of an interaction between dynamin 3 and Homer proteins (22), it was recently shown that dynamin 3 is present in dendritic spines of hippocampal neurons where it forms, in contrast to dynamin 1, a complex with Homer proteins and mGluR5 (41). However, coexpression of an epitope-tagged mGluR5 with a putative dominant-negative form of dynamin 3 (containing a mutation in the GTPase domain) did not affect mGluR5 internalization, indicating that dynamin 3 is not involved in mGluR5 trafficking (41).…”

SNX9 Regulates Dynamin Assembly and Is Required for Efficient Clathrin-mediated Endocytosis

“…However, dynamin-2 may also be involved in vesicle formation at the Golgi Kreitzer et al, 2000), in regulating actin dynamics (Schafer, 2004), in cell signaling (Kranenburg et al, 1999;Fish et al, 2000), and has recently been localized to the centriole (Thompson et al, 2004). Dynamin-3, which is most highly expressed in testis but also detectable in neurons (Gray et al, 2003) and in lung (Nakata et al, 1993), has been less well studied.…”

“…However, dynamin-2 may also be involved in vesicle formation at the Golgi Kreitzer et al, 2000), in regulating actin dynamics (Schafer, 2004), in cell signaling (Kranenburg et al, 1999;Fish et al, 2000), and has recently been localized to the centriole (Thompson et al, 2004). Dynamin-3, which is most highly expressed in testis but also detectable in neurons (Gray et al, 2003) and in lung (Nakata et al, 1993), has been less well studied.Dynamins are atypical GTPases, distinguished by their large size, low affinity for GTP, and high intrinsic rates of GTP hydrolysis (Sever et al, 2000b;Song and Schmid, 2003). Moreover, dynamin can self-assemble in solution (Hinshaw and Schmid, 1995) or on liposome templates into rings and spiral-like structures (Stowell et al, 1999).…”