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Biomedical subjects

F Casagrande

Publications and source records attributed to F Casagrande.

29 records · Page 2Linked to original sources
PubMed1998

Phosphatidylinositol 3-kinase inhibitors block aortic smooth muscle cell proliferation in mid-late G1 phase: effect on cyclin-dependent kinase 2 and the inhibitory protein p27KIP1.

In the present study, we investigated the involvement of phosphatidylinositol 3-kinase (PI 3-kinase) activity in the progression of vascular smooth muscle cells (VSMCs) throughout the G1 phase of cell cycle. Addition of two selective inhibitors of PI 3-kinase, LY 294002 or wortmannin, to quiescent VSMCs prevented serum-induced DNA synthesis in a dose-dependent manner with IC50 of 8.7 +/- 2.0 microM and 53.9 +/- 8.5 nM, respectively. Time course studies revealed that the two PI 3-kinase inhibitors blocked VSMC proliferation in mid-late G1 phase, about 6 h before the G1/S transition. This G1 growth arrest was due, at least in part, to the reduction of the CDK2 associated kinase activity resulting mainly from the upregulation of the inhibitory protein p27KIP1.

Androstadienes↗
PubMed1998

G1 phase arrest by the phosphatidylinositol 3-kinase inhibitor LY 294002 is correlated to up-regulation of p27Kip1 and inhibition of G1 CDKs in choroidal melanoma cells.

We have investigated the effect of the flavonoid derivative LY 294002, a potent and selective phosphatidylinositol 3-kinase inhibitor, on cell cycle progression in human choroidal melanoma cells. We demonstrate that LY 294002 induces a specific G1 block in asynchronously growing cells leading to an almost complete inhibition of cell proliferation after three days of treatment. When melanoma cells are released from a nocodazole-induced G2/M block, LY 294002 is shown to delay and greatly restrain the G1/S transition. The inhibitor is able to exert its action as long as it is added during the G1 progression and before the cells enter in S phase. We report that the LY 294002-induced G1 arrest is closely correlated to inhibition of CDK4 and CDK2 activities leading to the impairment of pRb phosphorylation which normally occurs during G1 progression. While the inhibition of CDK4 may be attributed at least in part to the decline in CDK4 protein level, CDK2 activity reduction is rather due to the up-regulation of the CDK inhibitor p27Kip1 and to its increased association to CDK2.

CDC2-CDC28 Kinases↗
PubMed1998

Differential expression of G1 cyclins and cyclin-dependent kinase inhibitors in normal and transformed melanocytes.

PURPOSE: To investigate the levels of the different regulatory proteins involved in the G1 progression and G1/S transition in normal and transformed human choroidal melanocytes (CM). METHODS: Three choroidal melanoma cell lines and three CM cultures were used. The purity of the CM cultures was assessed by different approaches, including morphologic study, specific immunostaining, cell proliferation behavior, and transforming growth factor-beta1 responsiveness. The cell cycle protein levels were evaluated by specific immunoblotting of total extracts obtained from the different cell lines. RESULTS: Alterations were observed in the expression of cylins D1 and E in the transformed cells, whereas the amounts of the cyclin-dependent kinases (CDKs) CDK2 and CDK4 were almost identical in both cell types. Although the expression of cyclin H was slightly increased in transformed cells, neither the CDK7 level nor the CDK7 and cyclin H localizations were altered when compared with those in normal CM. The results suggest the absence of the CDK inhibitor (CKI) p21 in two of the three melanoma cell lines and, as a main feature, a striking underexpression of p27 in the three transformed cell lines. Finally, although the p16 level was almost the same in normal and transformed cells, a loss of p16-CDK4 interaction was observed in two of the three melanoma cell lines. CONCLUSIONS: Deregulated expression of G1 cyclins and CKIs and alteration in the interaction of CKIs with CDKs may be implicated in the neoplastic transformation of human ocular melanocytes to malignant melanoma cells.

Cell Division↗
PubMed1983

The complete amino acid sequence of the Zn2+-containing D-alanyl-D-alanine-cleaving carboxypeptidase of streptomyces albus G.

The 22076-Mr Zn2+-containing D-alanyl-D-alanine-cleaving carboxypeptidase of Streptomyces abuls G effectively catalyses the transfer of the N alpha, N epsilon-diacetyl-L-lysyl-D-alanyl electrophilic group of the standard tripeptide substrate N alpha, N epsilon-diacetyl-L-lysyl-D-alanyl-D-alanine to water. It also performs a weak beta-lactamase activity, hydrolysing penicillin into penicilloate at a very low rate. This protein consists of 212 amino acid residues in a single polypeptide chain. The N terminus is partially blocked as a result of the cyclization of the dipeptide Asn-Gly into anhydroaspartylglycine imide. The protein has been fragmented by cyanogen bromide into five fragments whose sequences have been determined via appropriate subcleavages with various proteases. The ordering of the cyanogen bromide peptide fragments has been carried out (a) by submitting the S-carboxymethylated protein to complete tryptic digestion and labelling the methionine-containing peptides thus obtained with iodo[14C]-acetamide, and (b) by submitting to limited tryptic digestion the S-[2-(4'-pyridyl)ethyl]-cysteine protein whose amino groups have been blocked by reaction with exo-cis-3,6-endoxo-delta 4-tetrahydrophthalic anhydride prior to digestion. The protein contains six cysteine residues in the form of three disulfide bridges. No homology is found by comparing this peptidase with other Zn2+-containing enzymes (carboxypeptidase A, thermolysin, carbonic anhydrase B and alcohol dehydrogenase) and several completely or partially sequenced, serine-containing D-alanyl-D-alanine-cleaving peptidases and Zn2+/serine-containing beta-lactamases.

Amino Acid Sequence↗