cyclin-d1 and Glomerulosclerosis--Focal-Segmental

Cyclin D1 plays significant roles in cell cycle entry and migration. We have documented that both integrin α3β1 expressions and the number of podocytes were reduced in focal segmental glomerulosclerosis. We wondered whether integrin-extracellular matrix (ECM) interaction was involved in the regulation of cyclin D1 expression, and the possible signaling pathways in mitogen-stimulating podocytes. Cultured podocytes were divided into serum (mitogens/growth factors)-starved and serum-stimulated groups. Reverse transcription polymerase chain reaction was used to detect cyclin D1 mRNA, and Western blot analysis was used to measure protein concentrations of cyclin D1 and extracellular signal-regulated kinase (ERK) activation (p-ERK/ERK). The integrin-ECM interaction was blocked by anti-β1-integrin monoclonal antibody or RGDS (Arg-Gly-Asp-Ser). The MEK inhibitor, U0126, was used to inhibit ERK activation. The results showed that there was little cyclin D1 protein in serum-starved groups, but it was abundant in serum-stimulated groups. Both cyclin D1 mRNA and protein levels were reduced in serum-stimulated podocytes after blocking integrin-ECM interaction. ERK activation in serum-stimulated podocytes was significantly decreased after blocking integrin-ECM interaction. Cyclin D1 mRNA and protein concentrations in serum-stimulated podocytes were reduced after blocking ERK activation by U0126. We demonstrate that integrin-ECM interaction collaborates with mitogens to activate ERK/mitogen-activated protein kinase pathways which are essential for cyclin D1 expression in podocytes.

Topics: Animals; Antibodies, Monoclonal; Butadienes; Cyclin D1; Extracellular Matrix; Extracellular Signal-Regulated MAP Kinases; Glomerulosclerosis, Focal Segmental; Integrins; MAP Kinase Signaling System; Mitogens; Nitriles; Podocytes; Rats; Rats, Sprague-Dawley; RNA, Messenger

To investigate the morphological characteristics and expression of cell cycle regulatory proteins in cellular variants of idiopathic focal segmental glomerulosclerosis (FSGS).. Seventeen cases of cellular variants of FSGS were studied by light microscopy, immunofluorescence (IF), and electron microscopy (EM). The immunohistochemistry and immunoelectron microscopy for the detection of cyclins (cyclin D1, cyclin E, cyclin A, cyclin B1) and cyclin dependent kinase inhibitors (CKIs, including p21, p27, p57) were performed in these cases.. The hypertrophy and hyperplasia of epithelial cells overlying sclerotic or collapsed glomerular tufts were the prominent characteristics of cellular variants of FSGS; IF showed segmental deposits of IgM; hyperplastic epithelial cells possessed the features of both podocyte and parietal epithelial cells ultrastructurally. Hyperplastic epithelial cells of cellular lesions showed positive staining for cyclin E, cyclin A, cyclin B1 and p21, and negative staining for cyclin D1, p27 and p57.. The hyperplastic epithelial cells in cellular variants of FSGS may be derived from damaged podocytes, which mimic the immature podocytes, re-engage the cell cycle to proliferate and form the cellular lesions. The up-regulation of cyclins (cyclin E, cyclin A, cyclin B1) concurrent with the loss of CKIs (p27, p57) contributes to the cell cycle regulation of cellular lesions of FSGS.

Topics: Adolescent; Adult; Aged; Cell Cycle Proteins; Cyclin B; Cyclin B1; Cyclin D1; Cyclin-Dependent Kinase Inhibitor p27; Cyclin-Dependent Kinase Inhibitor p57; Female; Glomerulosclerosis, Focal Segmental; Humans; Immunohistochemistry; Male; Microscopy, Electron; Middle Aged; Nuclear Proteins; Tumor Suppressor Proteins