A cytoplasmic motif targets neuroligin-1 exclusively to dendrites of cultured hippocampal neurons.
The formation of neuronal synapses is thought to depend on trans-synaptic interactions between cell adhesion molecules (CAMs) on the surface of axons and dendrites. Synapses are highly asymmetric structures. Pre- and post-synaptic domains might therefore be assembled around heterophilic CAMs which are polarized to axons vs. dendrites. We here investigated the targeting of neuroligin (NLG)-1, a heterophilic CAM, which promotes synapse formation through interaction with its receptor beta-neurexin in axons. We demonstrate that NLG-1 is highly polarized to the dendritic plasma membrane. Dendritic targeting relies on a cytoplasmic amino acid motif. By expressing chimeras of NLG-1 and CD8, an unpolarized protein, we show that the cytoplasmic domain of NLG-1 is necessary and sufficient for dendritic targeting. Furthermore, by truncation analysis we isolated a 32-amino-acid targeting motif. When appended to CD8 this cytoplasmic sequence is sufficient to direct exclusively dendritic localization of the protein. Analysis of yellow fluorescent protein-tagged NLG-1 revealed that vesicular structures containing NLG-1 are excluded from the axon indicating that polarized distribution may be achieved by direct dendritic transport. We propose that the strict polarity of NLG-1 contributes to the directional assembly of synapses during development of the central nervous system.
Rosales
Carlos R
CR
Department of Biological Sciences, California State University Polytechnic, Pomona, CA, USA.
Osborne
Kyle D
KD
Zuccarino
Griselda V
GV
Scheiffele
Peter
P
Silverman
Michael A
MA
D000818:Animals; D001426:Bacterial Proteins / Q000378:metabolism; D016827:CD8 Antigens / Q000378:metabolism; D015816:Cell Adhesion Molecules, Neuronal; D002478:Cells, Cultured; D003593:Cytoplasm / Q000378:metabolism*; D003712:Dendrites / Q000378:metabolism*; D004622:Embryo, Mammalian; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006624:Hippocampus / Q000166:cytology*; D008164:Luminescent Proteins / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism*; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D016296:Mutagenesis / Q000502:physiology; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D009474:Neurons / Q000166:cytology*; D017434:Protein Structure, Tertiary; D051381:Rats; D014162:Transfection / Q000379:methods
D001426:Bacterial Proteins; D016827:CD8 Antigens; D015816:Cell Adhesion Molecules, Neuronal; D008164:Luminescent Proteins; C489787:MAP2 protein, rat; D008565:Membrane Proteins; D008869:Microtubule-Associated Proteins; D009419:Nerve Tissue Proteins; C093438:neuroligin 1; C054562:yellow fluorescent protein, Bacteria; D049452:Green Fluorescent Proteins