Immobilized pool of NCAM180 in the postsynaptic membrane is homeostatically replenished by the flux of NCAM180 from extrasynaptic regions.

TY - JOUR

T1 - Immobilized pool of NCAM180 in the postsynaptic membrane is homeostatically replenished by the flux of NCAM180 from extrasynaptic regions.

AU - Leshchyns´ka, Iryna

AU - Tanaka, Mark M

AU - Schachner, Melitta

AU - Sytnyk, Vladimir

PY - 2011

Y1 - 2011

N2 - Homeostatic mechanisms maintaining high levels of adhesion molecules in synapses over prolonged periods of time remain incompletely understood. We used fluorescence recovery after photobleaching experiments to analyze the steady state turnover of the immobile pool of green fluorescent protein-labeled NCAM180, the largest postsynaptically accumulating isoform of the neural cell adhesion molecule (NCAM). We show that there is a continuous flux of NCAM180 to the postsynaptic membrane from nonsynaptic regions of dendrites by diffusion. In the postsynaptic membrane, the newly delivered NCAM180 slowly intermixes with the immobilized pool of NCAM180. Preferential immobilization and accumulation of NCAM180 in the postsynaptic membrane is reduced after disruption of the association of NCAM180 with the spectrin cytoskeleton and in the absence of the homophilic interactions of NCAM180 in synapses. Our observations indicate that the homophilic interactions and binding to the cytoskeleton promote immobilization of NCAM180 and its accumulation in the postsynaptic membrane. Flux of NCAM180 from extrasynaptic regions and its slow intermixture with the immobile pool of NCAM180 in the postsynaptic membrane may be important for the continuous homeostatic replenishment of NCAM180 protein at synaptic contacts without compromising the long term synaptic contact stability.

AB - Homeostatic mechanisms maintaining high levels of adhesion molecules in synapses over prolonged periods of time remain incompletely understood. We used fluorescence recovery after photobleaching experiments to analyze the steady state turnover of the immobile pool of green fluorescent protein-labeled NCAM180, the largest postsynaptically accumulating isoform of the neural cell adhesion molecule (NCAM). We show that there is a continuous flux of NCAM180 to the postsynaptic membrane from nonsynaptic regions of dendrites by diffusion. In the postsynaptic membrane, the newly delivered NCAM180 slowly intermixes with the immobilized pool of NCAM180. Preferential immobilization and accumulation of NCAM180 in the postsynaptic membrane is reduced after disruption of the association of NCAM180 with the spectrin cytoskeleton and in the absence of the homophilic interactions of NCAM180 in synapses. Our observations indicate that the homophilic interactions and binding to the cytoskeleton promote immobilization of NCAM180 and its accumulation in the postsynaptic membrane. Flux of NCAM180 from extrasynaptic regions and its slow intermixture with the immobile pool of NCAM180 in the postsynaptic membrane may be important for the continuous homeostatic replenishment of NCAM180 protein at synaptic contacts without compromising the long term synaptic contact stability.

KW - Animals

KW - Cells, Cultured

KW - Mice

KW - Mice, Knockout

KW - Neural Cell Adhesion Molecules/genetics/metabolism

KW - Nerve Tissue Proteins/genetics/metabolism

KW - Protein Isoforms/genetics/metabolism

KW - Spectrin/genetics/metabolism

KW - Synaptic Membranes/genetics/metabolism

KW - Animals

KW - Cells, Cultured

KW - Mice

KW - Mice, Knockout

KW - Neural Cell Adhesion Molecules/genetics/metabolism

KW - Nerve Tissue Proteins/genetics/metabolism

KW - Protein Isoforms/genetics/metabolism

KW - Spectrin/genetics/metabolism

KW - Synaptic Membranes/genetics/metabolism

M3 - SCORING: Journal article

VL - 286

SP - 23397

EP - 23406

JO - J BIOL CHEM

JF - J BIOL CHEM

SN - 0021-9258

IS - 26

M1 - 26

ER -