Laminin-8/9 is synthesized by rat glomerular mesangial cells and is required for PDGF-induced mesangial cell migration.
BACKGROUND
Laminin (LM), the major glycoprotein component of basement membranes is expressed as multiple isoforms in a developmentally regulated and tissue-specific manner. LM alpha4 has a limited tissue distribution and is highly expressed in the developing glomerulus. In the present study, we investigate the in vivo and in vitro expression and function of LM alpha4 in the glomerulus.


METHODS
LM alpha4 expression was examined by Northern blot, reverse transcription polymerase chain reaction (RT-PCR), Western blot, and immunofluorescence microscopy. Mesangial cells (MC) were plated on purified LM-1, LM-2, and LM-8/9. Immunofluorescence microscopy was performed to examine the cellular phenotypes induced by LM-1 and LM-8/9. A modified Boyden chamber method was used to assess laminin participation in platelet-derived growth factor (PDGF)-stimulated migration.


RESULTS
mRNA for LMalpha4 is expressed in cultured rat MC, and isolated rat and mouse glomeruli, but not in cultured rat glomerular epithelial cells or glomerular endothelial cells. Using antibodies specific for LM alpha4, a 240 kD band was detected in MC extract and a slightly smaller band was identified in extracted rat glomeruli. Purified LM-8/9 had MC adhesive activity comparable to LM-1 and LM-2. MC attached to LM-8/9 exhibited a unique phenotype. In contrast to LM-1, attachment of MC to LM-8/9 produced a highly arborized cell morphology with significantly reduced formation of focal contacts or stress fibers. LM alpha4 is utilized by MC during PDGF-stimulated migration.


CONCLUSIONS
LM alpha4 is synthesized by MC and persists in the mature glomerulus. LM-8/9 stimulates a unique cellular morphology, and they are utilized in PDGF-induced migration. These factors suggest that LM alpha4 plays an important role in MC differentiation and in the maintenance of MC phenotype.
Hansen
Kim
K
Division of Nephrology, Department of Medicine, University of Washington School of Medicine, Seattle, Washington, USA.
Abrass
Christine K
CK
D000818:Animals; D002465:Cell Movement / Q000502:physiology; D002478:Cells, Cultured; D005920:Glomerular Mesangium / Q000166:cytology / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D066298:In Vitro Techniques; D007797:Laminin / Q000378:metabolism* / Q000502:physiology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D010641:Phenotype; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley
C501370:Lama4 protein, mouse; D007797:Laminin; D010982:Platelet-Derived Growth Factor; C110308:laminin 8; C404084:laminin 9