Glomerular proteins related to slit diaphragm and matrix adhesion in the foot processes are highly tyrosine phosphorylated in the normal rat kidney.
BACKGROUND
Tyrosine phosphorylation of proteins has been a focus of extensive studies since it plays crucial roles in regulation of diverse biological reactions. To understand the involvement of tyrosine phosphorylation in kidney functions, a comprehensive proteomic study for tyrosine-phosphorylated proteins was performed in the normal rat kidney.


METHODS
Two-dimensional gel electrophoresis and immunoprecipitation using anti-phosphotyrosine antibodies were employed to detect tyrosine-phosphorylated proteins. The proteins were analysed by mass spectrometry and validated by immunological analyses using specific antibodies.


RESULTS
Most of tyrosine-phosphorylated proteins were confined to the glomerulus and predominantly localized along the glomerular capillary wall, especially in the foot processes of podocytes. Our systematic proteomic analysis identified nephrin, SHPS-1 (tyrosine-protein phosphatase non-receptor-type substrate 1), FAK1 and paxillin as major tyrosine-phosphorylated proteins and Neph1, talin and vinculin as minor tyrosine-phosphorylated proteins. In the present study, SHPS-1 was identified as a novel tyrosine-phosphorylated protein in the glomerulus and was also predominantly localized at the foot processes. Mass spectrometric analysis identified in vivo phosphorylation sites of SHPS-1 on Y460, Y477 and Y501.


CONCLUSIONS
This study identified tyrosine-phosphorylated proteins in normal rat kidney, which were prominently rich in the glomerulus and localized at the podocyte foot processes. These proteins were categorized as cell-to-cell or cell-to-matrix adhesion complex-related molecules, suggesting their pivotal roles in the glomerular ultrafiltration.
Zhang
Ying
Y
Department of Structural Pathology, Institute of Nephrology, Graduate School of Medical and Dental Sciences, Niigata University, Niigata, Japan.
Yoshida
Yutaka
Y
Nameta
Masaaki
M
Xu
Bo
B
Taguchi
Izumi
I
Ikeda
Takako
T
Fujinaka
Hidehiko
H
Magdeldin
Sameh
S
Mohamed
Sameh Magdeldin
SM
Tsukaguchi
Hiroyasu
H
Harita
Yutaka
Y
Yaoita
Eishin
E
Yamamoto
Tadashi
T
D000818:Animals; D001665:Binding Sites; D015153:Blotting, Western; D015815:Cell Adhesion Molecules / Q000378:metabolism; D015180:Electrophoresis, Gel, Two-Dimensional; D051417:Focal Adhesion Kinase 1 / Q000737:chemistry / Q000378:metabolism; D007150:Immunohistochemistry; D047468:Immunoprecipitation; D007668:Kidney / Q000378:metabolism* / Q000648:ultrastructure; D007678:Kidney Glomerulus / Q000378:metabolism / Q000648:ultrastructure; D008297:Male; D013058:Mass Spectrometry; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism; D016253:Microscopy, Immunoelectron; D051419:Paxillin / Q000737:chemistry / Q000378:metabolism; D010766:Phosphorylation; D050199:Podocytes / Q000378:metabolism / Q000648:ultrastructure; D011506:Proteins / Q000737:chemistry* / Q000378:metabolism*; D040901:Proteomics; D051381:Rats; D017208:Rats, Wistar; D011971:Receptors, Immunologic / Q000737:chemistry / Q000378:metabolism; D014443:Tyrosine / Q000737:chemistry
D015815:Cell Adhesion Molecules; C486607:Kirrel1 protein, rat; D008565:Membrane Proteins; D051419:Paxillin; D011506:Proteins; C496063:Pxn protein, rat; D011971:Receptors, Immunologic; C501924:Sirpa protein, rat; D014443:Tyrosine; D051417:Focal Adhesion Kinase 1; C496052:Ptk2 protein, rat