Distribution of postsynaptic density proteins in rat kidney: relationship to neuronal nitric oxide synthase.
BACKGROUND
Neuronal nitric oxide synthase (nNOS) is expressed in skeletal muscle beneath the sarcolemma associated with dystrophin complex. In brain, nNOS is anchored to synaptic membranes by specific postsynaptic density proteins (PSD)-95 and PSD-93. We have investigated the cellular and subcellular localization of these PSD proteins in the kidney and their relationship to nNOS and the cell membrane.


METHODS
Kidneys from male Sprague-Dawley rats were processed for light and electron microscopic immunohistochemistry with polyclonal antibodies against PSD and nNOS proteins.


RESULTS
Western blot analysis of rat kidney revealed a specific band for PSD-93 at the molecular weight of 103 kDa. Immunostaining for PSD-93 was located in the thick ascending limb of the loop of Henle, macula densa cells, distal convoluted tubules, cortical collecting ducts, outer and inner medullary collecting duct, glomerular epithelium, and Bowman's capsule. A pre-embedding electron microscopic immunoperoxidase procedure localized PSD-93 to the basolateral membrane of these tubular cells. Using different sized immunogold particles, a portion of nNOS in the macula densa colocalized with PSD-93 adjacent to cytoplasmic vesicles and the basolateral membrane. In contrast, PSD-95 protein was detected only weakly in the cortex by Western blot. Immunostaining for PSD-95 was located only faintly in the apical membrane of the thick ascending limb, macula densa, distal convoluted tubule and cortical collecting duct cells.


CONCLUSIONS
PSD-93 is the predominant PSD expressed in the rat kidney. It is located primarily in the basolateral membranes of distal nephron and colocalizes with a pool of nNOS in cytoplasmic vesicles and basolateral membranes of macula densa cells.
Tojo
A
A
Division of Nephrology and Endocrinology, University of Tokyo, Japan.
Bredt
D S
DS
Wilcox
C S
CS
D000818:Animals; D000076122:Disks Large Homolog 4 Protein; D007150:Immunohistochemistry; D047908:Intracellular Signaling Peptides and Proteins; D007668:Kidney / Q000378:metabolism* / Q000648:ultrastructure; D008297:Male; D008565:Membrane Proteins; D016253:Microscopy, Immunoelectron; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000378:metabolism*; D052248:Nitric Oxide Synthase Type I; D020033:Protein Isoforms / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D014018:Tissue Distribution
D000076122:Disks Large Homolog 4 Protein; C501449:Dlg4 protein, rat; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; C501451:Mpp2 protein, rat; D009419:Nerve Tissue Proteins; D020033:Protein Isoforms; C033652:postsynaptic density proteins; D019001:Nitric Oxide Synthase; D052248:Nitric Oxide Synthase Type I; C496322:Nos1 protein, rat