RESUMO
We reported previously the enhanced phosphoinositide metabolism and constitutive activation of phosphoinositide-specific phospholipase C (PLC) in two colorectal carcinoma cell lines, KMS-4 and KMS-8, derived from familial adenomatous polyposis patients. To study the physiological role of enhanced PLC activity in these cells, we analyzed the effect of PLC inhibitor (PCI) peptides on their growth and cell cycle. N-Myristoylated PCI peptide, myr-PCI(Y), originally developed based on the PCI sequence of PLC-gamma 2, inhibited activity of purified PLC isoforms in vitro. When myr-PCI(Y) was added to KMS-4 and KMS-8 cultures, it suppressed the production of inositol trisphosphate, DNA synthesis, and cell growth, all of which were induced by serum in both KMS-4 and KMS-8 cells. The number of colonies grown in soft agar was also reduced significantly by treating KMS-8 cells with myr-PCI(Y) peptide. Flow cytometry analysis with propidium iodide labeling revealed marked decreases in the percentage of KMS-8 cells in S phase and increases in G0-G1 by the addition of myr-PCI(Y). On the other hand, myr-PCI(F), in which two of the tyrosine residues in myr-PCI(Y) are replaced by phenylalanine and which does not inhibit phosphatidylinositol 4,5-bisphosphate-hydrolyzing activity in vitro, did not significantly inhibit either inositol trisphosphate production or cell growth. These results indicate that the activation of PLC is essential for growth and the transformed properties of these colorectal carcinoma cells.
Assuntos
Polipose Adenomatosa do Colo , Carcinoma/metabolismo , Neoplasias Colorretais/metabolismo , Inibidores Enzimáticos/farmacologia , Oligopeptídeos/farmacologia , Fosfolipases Tipo C/antagonistas & inibidores , Sequência de Aminoácidos , Sangue , Carcinoma/enzimologia , Carcinoma/patologia , Ciclo Celular/efeitos dos fármacos , Divisão Celular/efeitos dos fármacos , Transformação Celular Neoplásica/efeitos dos fármacos , Neoplasias Colorretais/enzimologia , Neoplasias Colorretais/patologia , DNA de Neoplasias/biossíntese , Inibidores Enzimáticos/síntese química , Humanos , Fosfatos de Inositol/biossíntese , Dados de Sequência Molecular , Ácido Mirístico , Ácidos Mirísticos/química , Oligopeptídeos/síntese química , Transdução de Sinais/fisiologia , Células Tumorais Cultivadas , Fosfolipases Tipo C/química , Fosfolipases Tipo C/fisiologiaRESUMO
Calcium dependent proteases (calpains, CAPNs, E.C.3.4.22.17) constitute a family of proteins which share a homologous cysteine-protease domain (large subunits, L1, L2, and L3) and an E-F hand Ca2(+)-binding domain (L1, L2, L3, and small subunit, S). We have mapped the genes for four calpain proteins (L1, L2, L3, and S) on four distinct human chromosomes by a combination of spot-blot hybridization to flow-sorted chromosomes and Southern hybridization of DNAs from a human x mouse hybrid cell panel. The genes for calpain L1 (CAPN1, large subunit of calpain I), L2 (CAPN2, large subunit of calpain II), L3 (CAPN3, a protein related to the large subunits), and S (CAPN4, a small subunit common to calpains I and II) were assigned to human chromosomes 11, 1, 15, and 19, respectively.
