Overexpression of phosphorylated STAT-1alpha in the labial salivary glands of patients with Sjögren's syndrome.
OBJECTIVE
To clarify the molecular mechanisms of Sjögren's syndrome (SS), we analyzed the functional role of the STAT-1 gene, one of the interferon-gamma (IFNgamma)-inducible genes, in labial salivary glands (LSGs) from SS patients.


METHODS
The expression of STAT-1 messenger RNA (mRNA) was examined by real-time polymerase chain reaction (PCR) analysis, and the phosphorylation of STAT-1 protein (Tyr(701) and Ser(727) pSTAT-1) was investigated by Western blot and immunohistochemical analyses. The expression of IFNgamma-inducible 10-kd protein (IP-10), IFN regulatory factor 1 (IRF-1), and Fas was also examined by real-time PCR and immunohistochemical analyses.


RESULTS
STAT-1alpha and STAT-1beta mRNA were highly expressed in LSGs from SS patients. The level of STAT-1alpha protein in SS LSGs was higher than that in 3 control LSGs, whereas STAT-1beta protein was not clearly detected by Western blot analysis. Moreover, Tyr(701) and Ser(727) pSTAT-1alpha proteins were specifically detected in SS LSGs. Immunohistochemical analysis showed localization of Tyr(701) pSTAT-1 in infiltrating lymphocytes and the adjacent ductal epithelium from SS patients. Ser(727) pSTAT-1 was localized only in the ductal epithelium of SS LSGs. The STAT-1-inducible genes IP-10 and IRF-1 and the Fas genes were highly expressed in SS LSGs and were colocalized with Ser(727) pSTAT-1-positive, but not Tyr(701) pSTAT-1-positive, cells.


CONCLUSIONS
We found evidence of the up-regulation of STAT-1alpha mRNA and protein in LSGs from SS patients, as well as the presence of pSTAT-1alpha in ductal epithelium from SS patients. Our findings suggest that STAT-1alpha, especially Ser(727) pSTAT-1, may function as a key molecule in the pathogenesis of SS.
Wakamatsu
Ei
E
University of Tsukuba, Tsukuba City, Ibaraki 305-8575, Japan.
Matsumoto
Isao
I
Yasukochi
Takanori
T
Naito
Yusuke
Y
Goto
Daisuke
D
Mamura
Mizuko
M
Ito
Satoshi
S
Tsutsumi
Akito
A
Sumida
Takayuki
T
D015870:Gene Expression; D020022:Genetic Predisposition to Disease; D006801:Humans; D050832:Interferon-Stimulated Gene Factor 3 / Q000235:genetics* / Q000378:metabolism*; D010766:Phosphorylation; D012333:RNA, Messenger / Q000378:metabolism; D050794:STAT1 Transcription Factor / Q000235:genetics / Q000378:metabolism; D050795:STAT2 Transcription Factor / Q000235:genetics / Q000378:metabolism; D018987:Salivary Ducts / Q000378:metabolism / Q000473:pathology; D012470:Salivary Glands, Minor / Q000378:metabolism* / Q000473:pathology; D012694:Serine / Q000378:metabolism; D012859:Sjogren's Syndrome / Q000235:genetics* / Q000378:metabolism* / Q000473:pathology; D014443:Tyrosine / Q000378:metabolism
D050832:Interferon-Stimulated Gene Factor 3; D012333:RNA, Messenger; D050794:STAT1 Transcription Factor; C494079:STAT1 protein, human; D050795:STAT2 Transcription Factor; C494084:STAT2 protein, human; C079868:gamma interferon activation factor; D014443:Tyrosine; D012694:Serine