Distribution of the scaffolding proteins PSD-95, PSD-93, and SAP97 in isolated PSDs.
We compared the distribution of three scaffolding proteins, all belonging to a family of membrane-associated guanylate kinases, thought to have key roles in the organization of the postsynaptic density (PSD). Isolated PSDs readily adhered to treated glass coverslips where they were labeled with immunogold and rotary shadowed for analysis by EM. The distribution of proteins within individual PSDs were measured by counting and mapping individual immunogold particles. PSD-95, as previously described, is distributed evenly throughout the PSD. We find here that PSD-93 has a nearly identical distribution suggesting that PSD-95 and PSD-93 could perform similar roles. SAP97, in contrast, is concentrated near edges of cleft sides of the PSDs, and in small clumps on their cytoplasmic sides. The homogenous distribution of PSD-95 and PSD-93 throughout the PSD is consistent with their being part of a backbone that stabilizes their various binding partners within the PSD. The distribution of SAP97 confirms that this protein is actually an integral component of the PSD, and suggests that it may have a role in inserting or stabilizing its main binding partner, Glu-R1, at the edge of the PSD.
DeGiorgis
Joseph A
JA
Laboratory of Neurobiology, National Institutes of Health, NINDS, Building 49, Room 3A60, 49 Convent Drive, Bethesda, MD 20892, USA. degiorgj@mail.nih.gov
Galbraith
James A
JA
Dosemeci
Ayse
A
Chen
Xiaobing
X
Reese
Thomas S
TS
D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D000818:Animals; D002451:Cell Compartmentation / Q000502:physiology; D003599:Cytoskeleton / Q000378:metabolism / Q000648:ultrastructure; D000076122:Disks Large Homolog 4 Protein; D007150:Immunohistochemistry / Q000379:methods*; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism*; D016253:Microscopy, Immunoelectron / Q000379:methods*; D051381:Rats; D017207:Rats, Sprague-Dawley; D018091:Receptors, AMPA / Q000378:metabolism; D013347:Subcellular Fractions / Q000378:metabolism / Q000648:ultrastructure; D013570:Synaptic Membranes / Q000378:metabolism* / Q000648:ultrastructure; D009435:Synaptic Transmission / Q000502:physiology
D048868:Adaptor Proteins, Signal Transducing; D000076122:Disks Large Homolog 4 Protein; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D018091:Receptors, AMPA; C501119:Dlg1 protein, rat; C501449:Dlg4 protein, rat; C501451:Mpp2 protein, rat