The
cytoskeletal proteins from erythrocytes, lymphoid cells, unstimulated and stimulated platelets, HeLa cells, and Ehrlich
ascites cells were prepared as
Triton X 100 insoluble residues. The pellet was extracted using the Bligh-Dyer procedure. After separation of the
lipids by thin-layer chromatography,
phospholipids and neutral
lipids were estimated and the
lipid pattern was compared with the
lipid composition of the total cell. The percentage of the
lipids associated with the
Triton X 100 insoluble pellet ranged between 10 and 50 depending on the
lipid and the cell type. Despite of the heterogenous
protein composition of the residue in the different cells involving microfilaments and intermediate filaments together with associated
proteins and minor components, in all cells sphingomyeline (Sph) and
free fatty acids (FA) could be found in outstanding contents. In HeLa cells we found beside the high proportion of Sph a different species pattern of diacyl-, alkylacyl-, and alkenylacyl classes of endogenous
diacylglycerol (DG),
phosphatidylcholine (PC), and
phosphatidylethanolamine (PE). The discussion involved the data from literature showing
lipid associations with all 3 classes of cytoskeletal filaments: microtubules, intermediate filaments, and microfilaments. These results were obtained by histological observation, by in vitro binding studies between
cytoskeletal proteins and purified
lipids, and--as we have practised--by
lipid analysis after extraction of the more or less purified cytoskeleton. Artefacts could not be excluded, but the different
lipid pattern in the total cell compared with the cytoskeletal let us assume that the results can not be explained by coprecipitation of
micelles or organelle remnants with the
Triton X 100 insoluble residue alone. An in vivo association of
lipids, mainly of Sph, with
F-actin and/or associated
proteins might be concluded.