Annulate lamellae and single pore complexes in normal, SV40-transformed and tumor cells in vitro: A semiquantitative analysis

Abstract

The frequency with which annulate lamellae (AL) and single cytoplasmic pore complexes appeared in selected groups (normal cell lines, SV40-, Rous sarcoma-, and 6 94 virus-infected cell lines, SV40-transformed cell lines, and both human and mouse tumor cell lines) was observed during standard electron microscopy techniques. All cell lines tested contained single pore complexes in the rough endoplasmic reticulum (RER). Further, it was found that at early passages WI38 cells have more single pore complexes than at later passages. In SV40-infected CV1 cells, the number of pore complexes increased during the infectious cycle, which indicates that the formation of these complexes may not be dependent on nuclear membrane remnants from mitosis. No pore complexes were found during mitosis, i.e., the formation of cytoplasmic pore complexes is by new synthesis or reformation. We speculate that all proliferating cells and germ cells generate pore complexes (similar to nuclear pore complexes) in their cytoplasmic membrane systems. With respect to annulate lamellae, it was found that: 1. (1) In cell lines where AL could be observed, not all cells exhibited AL stacks. 2. (2) “Normal” cells—such as human fetal lung (WI38) and monkey kidney (CV1) cells, mouse macrophages and fibroblasts, and cells from chicken explants—did not have AL stacks, but AL stacks could be induced by exposure to vinblastine. 3. (3) SV40-infected cells did not generate stacks of AL in the cell lines tested. 4. (4) SV40-transformed cells had AL stacks in a few cells or in many, depending on the cell line. 5. (5) The introduction of the SV40-containing chromosome 7 of human transformed LN-SV cells into a cell type that did not express AL formation caused it to form AL. 6. (6) AL were present up to 48 h after enucleation of mouse L cells, that is until the cells show signs of degeneration (which indicates that cellular upkeep of AL may not be dependent on the presence of the nucleus, as was suggested by the simultaneous disappearance of AL at mitosis). 7. (7) All tumor cell lines investigated were found to have AL stacks.