1: Am J Respir Cell Mol Biol. 2005 Jan;32(1):28-34. Epub 2004 Oct 28. 

Imbalanced plasminogen system in lymphangioleiomyomatosis: potential role of
serum response factor.

Zhe X, Yang Y, Schuger L.

Department of Pathology, Wayne State University, School of Medicine, Detroit,
Michigan 48201, USA.

Pulmonary lymphangioleiomyomatosis (LAM) is characterized by abnormal smooth
muscle-like cell (LAM cell) proliferation leading to tissue destruction. We
previously demonstrated that serum response factor (SRF), a critical smooth
muscle transcription factor, is highly expressed in LAM cells. Here we show that
a high SRF level alters the plasminogen (Plg) system. Specifically,
overexpression of SRF in human lung fibroblasts upregulated urokinase-type
plasminogen activator (uPA) and its substrate Plg, whereas it downregulated
plasminogen activator inhibitor (PAI)-1. Because uPA cleaves Plg into plasmin,
which activates matrix metalloproteinases (MMP), the end result was an increase
in MMP activity. To determine whether uPA, Plg, and PAI-1 were abnormally
expressed in LAM in vivo, we immunostained 12 LAM cases. In all cases, the LAM
lesions showed stronger immunoreaction for uPA and Plg than the surrounding
normal lung parenchyma. On the contrary, PAI-1 was absent in LAM lesions,
whereas it was ubiquitous in normal lung parenchyma. Microdissection-based
reverse transcriptase/polymerase chain reaction further confirmed upregulation
of uPA and Plg and downregulation of PAI-1 message in LAM. Altogether, our
findings suggest that the high SRF level seen in LAM contributes to
extracellular matrix degradation and progressive LAM cell infiltration of the
lung.

PMID: 15514113 [PubMed - indexed for MEDLINE]


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2: Thromb Haemost. 1999 May;81(5):767-74. 

Transcriptional regulation of the murine urokinase-type plasminogen activator
gene in skeletal myoblasts.

Miralles F, Ibanez-Tallon I, Parra M, Crippa M, Blasi F, Besser D, Nagamine Y,
Munoz-Canoves P.

Institut de Recerca Oncologica, Barcelona, Spain.

We have previously shown that urokinase-type plasminogen activator (uPA) is
highly expressed in murine C2C12 myoblasts and that antibodies against uPA are
able to block both myoblast fusion and differentiation. Here we show the
characterization of cis-acting elements in the mouse uPA promoter in vitro which
are involved in uPA gene expression in C2C 12 myoblast cells. DNase I
hypersensitive (HS) site analysis revealed the presence of three HS sites in
myoblasts. Deletion analysis of stably transfected uPA-promoter constructs
revealed that at least two of the three HS sites accounted for the high
transcriptional expression in C2C12 cells. One was located at -2.4 kb and
corresponded to a known PEA3/AP1A element and the other one was located at -4.9
kb and contained a CArG box and a CRE element. So far, no regulatory function
had been assigned to this CRE/CArG element. Both HS sites alone were able to
activate transcription of a heterologous promoter and showed a cooperative
effect when placed together. Electrophoretic mobility-shift assays using
myoblast nuclear extracts and specific antibodies demonstrated that cJun, JunD
and ATF2 bound to the PEA3/AP1A element, whereas the CRE/CArG element bound SRF.
Altogether, these results suggest that high uPA expression in myoblasts is
dependent on the cooperation of two regulatory sites in the uPA promoter.

PMID: 10365752 [PubMed - indexed for MEDLINE]


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