Biomedical subjects

M Luyten

Publications and source records attributed to M Luyten.

4 recordsLinked to original sources

PubMed1995

Distribution of calcineurin A isoenzyme mRNAs in rat thymus and kidney.

The distribution of the mRNAs encoding the different isoforms of the catalytic subunit (A subunit) of calcineurin has been investigated in rat thymus and kidney using in situ hybridization histochemistry with specific antisense oligonucleotide probes. In the thymus, the mRNAs of the A beta isoforms were the predominant transcripts and showed very intense hybridization signals in the cortical areas. The A alpha mRNAs were expressed at low levels. A beta 2 mRNA was expressed at higher levels than A beta 3 mRNA, but no difference could be detected between the expression levels of A alpha 1 and A alpha 2. In the kidney, highest calcineurin A mRNA hybridization signals were found in the medulla. Signal intensities of A alpha mRNAs were comparable to those of A beta mRNAs. A alpha 1 mRNA level was extremely weak, and A beta 2 mRNA expression was slightly higher than A beta 3 mRNA expression. A tissue-specific distribution pattern of the alternatively spliced isoforms of calcineurin A, as suggested by these preliminary data from thymus and kidney, may be critical in understanding the toxic side-effects associated with the use of the immunosuppressive, calcineurin-inhibiting compounds cyclosporin A and FK506.

Animals↗

PubMed1994

Solution structure of a cysteine rich domain of rat protein kinase C.

Intracellular protein phosphorylation by protein kinase C (PKC) plays a major role in the translation of extracellular signals into cellular events. Speculations on the structural basis for PKC activation are based on sequence homology between their cysteine-rich domains (CRD) and the DNA-binding 'zinc-fingers'. We produced a fragment comprising the second CRD (CRD2) of rat PKC-alpha and determined its three-dimensional structure in solution by NMR spectroscopy. This revealed that CRD2 adopts a globular fold allowing two non-consecutive sets of zinc-binding residues to form two separate metal-binding sites. The fold is different to those previously proposed and allows insight into the molecular topology of a family of homologous proteins.

Amino Acid Sequence↗

PubMed1993

Cyclosporins. Structure-activity relationships.

Cyclosporin A (Sandimmun) achieves immunosuppressive activity by complex formation with cyclophilin and subsequent binding of the binary complex to and inhibiting protein phosphatase 2B (calcineurin). Complexes of nonimmunosuppressive cyclophilin binding cyclosporin analogues do not inhibit protein phosphatase 2B, suggesting a crucial role for this enzyme in T cell activation. Binding of cyclosporin A to cyclophilins A, B, and C, respectively, results in complexes of significantly different inhibitory potency. The cyclosporin molecule thus has two functional domains, one mediating cyclophilin binding and a second one endowing affinity of the complex to calcineurin, thereby inhibiting its enzyme activity. Structure-activity studies and x-ray crystallography of cyclosporin-cyclophilin complexes indicate a crucial role of leucine side chains in positions 4 and 6 of the cyclosporin macrocycle for the calcineurin interaction.

Amino Acid Sequence↗

PubMed1993

Differential distribution of calcineurin A alpha isoenzyme mRNA's in rat brain.

Specific antisense oligonucleotide probes for the alpha isoforms of the catalytic subunit (A-subunit) of calcineurin were prepared and the distribution of A alpha 1 and A alpha 2 mRNA's has been studied in rat brain using in situ hybridization histochemistry. Clear regional differences have been observed for the A alpha 1 and A alpha 2 isoforms. The predominant form, A alpha 1, was found to be preferentially expressed in the caudate putamen, the pyramidal cell layer of the hippocampus, specific cortical cell layers, the cerebellar granular cell layer and some other brain areas. On the other hand, the A alpha 2 isoform, although being generally less abundant than A alpha 1, gave an intense autoradiography signal in the dentate gyrus of the hippocampus and was the major transcript in the amygdala, the superior and the inferior colliculus, the central gray matter and the reticular formation. These regional differences might reflect specific functions exerted by the two alternatively spliced isoenzymes in the CNS and opens the perspective of interfering with defined calcineurin-dependent signal transduction pathways using isoform-specific compounds.

Animals↗