Distinct structural forms of type I collagen modulate cell cycle regulatory proteins in mesangial cells.
BACKGROUND
Extracellular matrix molecules profoundly regulate cell behavior, including proliferation. In glomerulonephritis, type I collagen accumulates in the mesangium and is constantly structurally modified and degraded during the course of the disease.


METHODS
We studied how two structurally distinct forms of type I collagen, monomer versus polymerized fibrils, affect cell proliferation, mitogen-activated protein kinase (MAPK) activation, and expression of G1-phase regulatory proteins in cultured rat mesangial cells (MCs). To analyze the possible involvement of collagen-binding integrins in type I collagen-derived growth signals further, distribution patterns of integrin chains were examined by immunocytochemistry.


RESULTS
Polymerized type I collagen completely prevented the increase of DNA synthesis and cell replication induced by 5% fetal calf serum (FCS) or 25 ng/mL platelet-derived growth factor (PDGF) in MCs on monomer type I collagen. Protein expression of cyclins D1 and E was markedly down-regulated in MCs plated on polymerized type I collagen for eight hours in 5% FCS, as compared with MCs on monomer type I collagen. Incubation with 5% FCS reduced expression of the cdk-inhibitor protein p27Kip1 on monomer but not on polymerized type I collagen. Moreover, polymerized type I collagen markedly reduced cyclin E-associated kinase activity in the presence of 5% FCS. Polymerized type I collagen diminished the PDGF-induced phosphorylation and nuclear translocation of p42/p44 MAPK, but did not affect phosphorylation of PDGF beta-receptors. In MCs plated on monomer type I collagen, alpha1, alpha2, and beta1 integrin chains were recruited into focal contacts. However, on polymerized type I collagen, alpha2 and beta1, but not alpha1, integrin chains were condensed into focal contacts.


CONCLUSIONS
The growth-inhibitory effect of polymerized type I collagen is characterized by rapid changes of expression and/or activation of MAPK and G1-phase regulators and could result from the lack of alpha1beta1 integrin signaling in MCs on polymerized type I collagen. Conceivably, deposition of polymerized type I collagen might reflect a reparative response to control MC replication in glomerular inflammation.
Schöcklmann
H O
HO
Medizinische Klinik IV, Universität Erlangen-Nürnberg, Erlangen, Germany. Harald.Schoecklmann@t-online.de
Lang
S
S
Kralewski
M
M
Hartner
A
A
Lüdke
A
A
Sterzel
R B
RB
D000818:Animals; D001798:Blood Proteins / Q000494:pharmacology; D002448:Cell Adhesion / Q000502:physiology; D018797:Cell Cycle Proteins; D002467:Cell Nucleus / Q000201:enzymology; D002478:Cells, Cultured; D003094:Collagen / Q000737:chemistry / Q000378:metabolism*; D019927:Cyclin E / Q000378:metabolism; D050760:Cyclin-Dependent Kinase Inhibitor p27; D004247:DNA / Q000096:biosynthesis; D005109:Extracellular Matrix / Q000201:enzymology; D016193:G1 Phase / Q000187:drug effects / Q000502:physiology*; D005920:Glomerular Mesangium / Q000166:cytology* / Q000201:enzymology*; D005921:Glomerulonephritis / Q000378:metabolism / Q000473:pathology; D006965:Hyperplasia; D039222:Integrin alpha1beta1; D016023:Integrins / Q000378:metabolism; D008297:Male; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D010766:Phosphorylation; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D011108:Polymers / Q000378:metabolism; D011494:Protein Kinases / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D017479:Receptors, Platelet-Derived Growth Factor / Q000378:metabolism; D016196:S Phase / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology; D025521:Tumor Suppressor Proteins; D014443:Tyrosine / Q000378:metabolism
D001798:Blood Proteins; C493962:Cdkn1b protein, rat; D018797:Cell Cycle Proteins; D019927:Cyclin E; D039222:Integrin alpha1beta1; D016023:Integrins; D008869:Microtubule-Associated Proteins; D010982:Platelet-Derived Growth Factor; D011108:Polymers; D025521:Tumor Suppressor Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27; D014443:Tyrosine; D003094:Collagen; D004247:DNA; D011494:Protein Kinases; C102333:histone H1 kinase; D017479:Receptors, Platelet-Derived Growth Factor; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases