Photoexcited calphostin C selectively destroys nuclear lamin B1 in neoplastic human and rat cells - a novel mechanism of action of a photodynamic tumor therapy agent.

Abstract

Lamin B1, a major component of the nuclear lamina, anchors the nucleus to the cytoskeletal cage, and controls nuclear orientation, chromosome positioning and, alongside several enzymes, fundamental nuclear functions. Exposing polyomavirus-transformed rat pyF111 fibroblasts and human cervical carcinoma (HCC) C4-I cells for 30 min to photoexcited perylenequinone calphostin C, i.e. Cal C(phiE), an established reactive oxygen species (ROS)-generator and protein kinase C (PKC) inhibitor, caused the cells to selectively oxidize and then totally destroy their nuclear lamin B1 by only 60 min after starting the treatment, i.e. when apoptotic caspases' activities had not yet increased. However, while the oxidized lamin B1 was being destroyed, lamins A/C, the lamin A-associated nuclear envelope protein emerin, and the nucleoplasmic protein cyclin E were neither oxidized nor destroyed. The oxidized lamin B was ubiquitinated and demolished in the proteasome probably by an enhanced peptidyl-glutaminase-like activity. Hence, the Cal C(phiE)-induced rapid and selective lamin B1 oxidation and proteasomal destruction ahead of the activation of apoptotic caspases was by itself a most severe molecular lesion impairing vital nuclear functions. Conversely, Cal C directly added to the cells kept in the dark damaged neither nuclear lamin B1 nor cell viability. Thus, our findings reveal a novel cell-damaging mechanism of a photodynamic tumor therapeutic agent.

• Authors: Anna Chiarini, James F Whitfield, Raffaella Pacchiana, Ubaldo Armato, Ilaria Dal Pra
• Journal: Biochimica et biophysica acta (Biochim Biophys Acta) Vol. 1783 Issue 9 Pg. 1642-53 (Sep 2008) ISSN: 0006-3002 [Print] Netherlands
• PMID: 18439918 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Antibiotics, Antineoplastic
• Lamin Type B
• Naphthalenes
• lamin B1
• Proteasome Endopeptidase Complex
• calphostin C

Topics

• Animals
• Antibiotics, Antineoplastic (pharmacology, radiation effects)
• Apoptosis
• Cell Line, Transformed
• Cell Line, Tumor
• Humans
• Immunohistochemistry
• Lamin Type B (analysis, immunology, metabolism)
• Naphthalenes (pharmacology, radiation effects)
• Neoplasms (metabolism, pathology)
• Nuclear Envelope (metabolism)
• Oxidative Stress
• Photochemotherapy
• Proteasome Endopeptidase Complex (metabolism)
• Rats
• Ubiquitination