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Structural association of Bax with nuclear matrix and cytomatrix revealed by embedment-free immunogold electron
B Gajkowska1, T Motyl, H Olszewska-Badarczuk
1Laboratory of the Cell Ultrastructure, Medical Research Centre, Polish Academy of Sciences, Warsaw, Poland. gajk@cmdik.pan.pl
Abstract:
Bax is a cellular protein functioning as a promoter of apoptosis. It is ultrastructurally associated with mitochondrial membranes, where it participates in permeability transition pore formation. By employing embedment-free electron microscopy (EFEM), we present evidence that Bax is also associated with the nuclear matrix and cytomatrix of cultured human tumour cells (COLO 205, PA-1, U-373 MG). Extracted cellular scaffolds were probed with anti-Bax antibody using the immunogold electron microscopy technique. Bax immunoreactivity was found on 10-15 nm intermediate filaments of karyo- and cytoskeleton, stretched between the nucleus, nuclear lamina and cell periphery. Bax immunoreactivity was preferentially localized to certain areas of filaments (spot-like). The target molecules for Bax binding in the cellular matrix and their physiological significance remain to be established.
Insights
Bax, a protein promoting cell death (apoptosis), is found on intermediate filaments within the nuclear and cellular matrix of human tumor cells. Its precise binding targets and roles in this location require further investigation.
Area of Science:
- Cell Biology
- Molecular Biology
- Cancer Research
Background:
- Bax is a known promoter of apoptosis, primarily localized to mitochondrial membranes.
- Its role in mitochondrial outer membrane permeabilization is crucial for programmed cell death.
Purpose of the Study:
- To investigate the ultrastructural localization of Bax beyond mitochondrial membranes.
- To explore potential novel roles of Bax in cellular architecture.
Main Methods:
- Embedment-Free Electron Microscopy (EFEM) was utilized to visualize cellular structures.
- Immunogold electron microscopy with anti-Bax antibody was employed on extracted cellular scaffolds.
Main Results:
- Bax was ultrastructurally associated with the nuclear matrix and cytomatrix in cultured human tumor cells.
- Bax immunoreactivity was observed on 10-15 nm intermediate filaments of the karyo- and cytoskeleton.
- Spot-like Bax localization was noted on these filaments, connecting the nucleus to the cell periphery.
Conclusions:
- Bax exhibits a novel association with the nuclear and cytoskeletal matrix.
- The specific binding molecules and physiological functions of Bax in these locations are yet to be determined.