• Bax;
  • DGD;
  • nuclear matrix;
  • cytomatrix;
  • EFEM

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 10–15nm 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.