Characterization of glucocorticoid-specific binding in the L2C leukemia.

Area of Science:

• Biochemistry
• Cell Biology
• Endocrinology

Background:

• L2C cells are a B-lymphocyte leukemia in guinea pigs.
• This leukemia is resistant to cortisol and adrenocorticotrophic hormone.
• Understanding glucocorticoid receptor binding is crucial for leukemia research.

Purpose of the Study:

• To characterize glucocorticoid-specific binding macromolecules in L2C cells.
• To determine the binding affinity and capacity of these receptors.
• To investigate the specificity and stability of the glucocorticoid receptor complex.

Main Methods:

• Cell harvesting via cardiac puncture and Ficoll:Hypaque separation.
• Cytosol preparation through sonication and ultracentrifugation.
• Glucocorticoid receptor quantification using hydroxylapatite assay and Sephadex G-25 chromatography.
• Whole-cell binding assays and nuclear translocation studies.

Main Results:

• Maximal specific binding of [3H]triamcinolone acetonide was 300 fmol/10(8) cells.
• Scatchard analysis revealed a Kd of 18 nM and 2000 binding sites/cell.
• Binding specificity: triamcinolone acetonide > dexamethasone > cortisol > progesterone > testosterone = estradiol.
• Receptor complex stable for 48 hr, sensitive to pronase and heat, but not DNase/RNase.
• Nuclear translocation of ~65% bound receptors upon temperature shift, without affecting cell viability.

Conclusions:

• L2C cells possess functional glucocorticoid receptors with specific binding properties.
• Receptor-hormone complex formation and translocation occur but do not induce cell death.
• These findings provide insights into glucocorticoid resistance mechanisms in leukemia.