SM22alpha: the novel phenotype marker of injured glomerular epithelial cells in anti-glomerular basement membrane nephritis.
OBJECTIVE
Our previous comprehensive analysis of the genes expressed in kidneys with anti-glomerular basement membrane (GBM) nephritis using DNA microarrays showed that SM22alpha was one of the highly expressed genes. SM22alpha is a 22-kDa cytoskeletal protein that is exclusively expressed in smooth muscle cells. We investigated the localization of SM22alpha at mRNA and protein levels, and its pathological significance in anti-GBM nephritis kidneys.


METHODS
Northern blot analysis, in situ hybridization, immunohistochemistry and double immunofluorescence studies were performed. The specific antibody (Ab) against SM22alpha was obtained by immunization of rabbits with recombinant rat SM22alpha protein.


RESULTS
SM22alpha mRNA expression was upregulated in kidneys and inducibly expressed in the parietal and visceral glomerular epithelial cells in anti-GBM nephritis kidneys. Immunohistochemistry with anti-SM22alpha Ab showed that SM22alpha protein was localized in the same series of cells. Double immunofluorescence with anti-SM22alpha and anti-glomerular cell markers demonstrated that SM22alpha might be expressed in epithelial cells of injured glomeruli. In visceral epithelial cells, SM22alpha might be expressed in cells in which podocyte specific markers, podocalyxin and nephrin were lost.


CONCLUSIONS
The injured glomerular epithelial cells in anti-GBM nephritis might undergo structural and functional alterations, including the expression of a smooth muscle marker, SM22alpha.
Ogawa
Asa
A
Division of Clinical Nephrology and Rheumatology, Institute of Nephrology, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan.
Sakatsume
Minoru
M
Wang
Xingzhi
X
Sakamaki
Yunichi
Y
Tsubata
Yutaka
Y
Alchi
Bassam
B
Kuroda
Takeshi
T
Kawachi
Hiroshi
H
Narita
Ichiei
I
Shimizu
Fujio
F
Gejyo
Fumitake
F
D000818:Animals; D001485:Basement Membrane / Q000276:immunology*; D015415:Biomarkers / Q000378:metabolism; D004195:Disease Models, Animal; D004847:Epithelial Cells / Q000378:metabolism* / Q000473:pathology; D005786:Gene Expression Regulation; D005921:Glomerulonephritis / Q000139:chemically induced / Q000378:metabolism* / Q000473:pathology; D007074:Immunoglobulin G; D007678:Kidney Glomerulus / Q000378:metabolism* / Q000473:pathology; D008297:Male; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D008840:Microfilament Proteins / Q000235:genetics / Q000378:metabolism*; D009124:Muscle Proteins / Q000235:genetics / Q000378:metabolism*; D020411:Oligonucleotide Array Sequence Analysis; D010641:Phenotype; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011897:Random Allocation; D051381:Rats; D011921:Rats, Inbred WKY; D012795:Sialoglycoproteins / Q000235:genetics / Q000378:metabolism
D015415:Biomarkers; D007074:Immunoglobulin G; D008565:Membrane Proteins; D008840:Microfilament Proteins; D009124:Muscle Proteins; D012333:RNA, Messenger; D012795:Sialoglycoproteins; C113267:nephrin; C001643:podocalyxin; C051615:transgelin