Intermediate filaments in monkey kidney TC7 cells: focal centers and interrelationship with other cytoskeletal systems

Two-dimensional gel electrophoresis of intermediate-sized filament-enriched cytoskeletons of epithelial monkey kidney TC7 cells has shown that they are composed of at least two keratins (isoelectric focusing 36, Mr = 48,500; IEF 46, Mr = 43,500; HeLa protein catalogue number) and vimentin. Indirect immunofluorescence as well as immunoelectron microscopy using antibodies directed against specific polypeptides sometimes revealed a discontinuous staining of keratin-containing filaments. Indirect immunofluorescence analysis of cells stained with keratin or vimentin antibodies also revealed a bright perinuclear staining in 58% of the cells in interphase. Of particular interest were focal centers from which filaments radiated. Double-label immunofluorescence using tubulin and keratin antibodies showed that these centers codistributed with focal arrays of microtubules (most likely centrosomes) in interphase cells but were not colocalized with centrioles in mitosis or, in many cases, with the microtubule organizing centers seen after release from nocodazole treatment. Treatment of TC7 cells with demecolcine (10 micrograms/ml, 20 hr) resulted in a drastic rearrangement of the keratin and vimentin filaments. Likewise, treatment with cytochalasin B (10 micrograms/ml, 1 hr) produced a star-like arrangement of the keratin and vimentin filaments and, in most cases, these codistributed with patches of actin. The results provide evidence for the interaction of intermediate filaments (keratins and vimentin) with both microtubules and microfilaments.

Phosphorylation of keratin and vimentin polypeptides in normal and transformed mitotic human epithelial amnion cells: behavior of keratin and vimentin filaments during mitosis

Analysis by means of two-dimensional gel electrophoresis (IEF) of [32P]orthophosphate-labeled proteins from mitotic and interphase transformed amnion cells (AMA) has shown that keratins IEF 31 (Mr = 50,000; Hela protein catalogue number), 36 (Mr = 48,500), 44 (Mr = 44,000), 46 (Mr = 43,500), as well as vimentin (IEF 26; Mr = 54,000) are phosphorylated above their interphase level during mitosis. Similar studies of normal human amnion epithelial cells (AF type) confirmed the above observations except in the case of keratin IEF 44 whose relative proportion was too low to be analyzed. Immunofluorescent staining of methanol/acetone-treated mitotic transformed amnion cells with a mouse polyclonal antibody elicited against human keratin IEF 31 showed a dotted staining (with a fibrillar background) in all of the cells in late anaphase/early telophase (characteristic "domino" pattern) and in a sizeable proportion of the cells in other stages of mitosis. Normal mitotic amnion cells on the other hand showed a fine fibrillar staining of keratins at all stages of mitosis. Similar immunofluorescent staining of normal and transformed mitotic cells with vimentin antibodies revealed a fibrillar distribution of vimentin in both cell types. Taken together the results indicate that the transformed amnion cells may contain a factor(s) that modulates the organization of keratin filaments during mitosis. This putative factor(s), however, is most likely not a protein kinase as transformed amnion cells and amnion keratins are modified to similar extents. It is suggested that in general the preferential phosphorylation of intermediate-sized filament proteins during mitosis may play a role in modulating the various proposed associations of these filaments with organelles and other cellular structures.

Differential immunological crossreactivity of HeLa keratin antibodies with human epidermal keratins

HeLa cells contain four keratin-like proteins having molecular weights of 50,000 (IEF 31), 48,500 (IEF 36), 44,000 (IEF 44), and 43,500 (IEF 46), respectively. Mouse polyclonal antibodies prepared against two of these keratins (IEF 31 and 46) have been used in this study to identify human epidermal keratins with common antigenic determinants. Using a sensitive immunoprecipitation procedure we show that the IEF 31 antibody crossreacts with three human acidic epidermal keratins, termed K1, K2, and K3, having molecular weights of 44,000, 47,500, and 54,000, respectively. One of these keratins (K1) comigrated with HeLa keratin IEF 44 and exhibited an identical one-dimensional peptide map. This protein is also abundant in basaliomas. In contrast to these results, the IEF 46 antibody showed no crossreactivity with any of the human acidic or basic [35S]methionine-labeled epidermal proteins. The lack of crossreactivity of this antibody was further confirmed by indirect immunofluorescence staining of cryostat sections from human split skin. These results emphasize both the similarity and diversity of antigenic determinants among HeLa and epidermal keratins.

Distribution of HeLa cells polypeptides in cytoplasts and karyoplasts

The polypeptide composition of cytoplasts and karyoplasts prepared form HeLa cells prelabelled with [35S]-methionine and enucleated with Cytochalasin B has been analyzed using high resolution two dimensional gel electrophoresis (IEF and NEPHGE). Of the 259 major proteins followed in this study we have identified 73 polypeptides (30 acidic(IEF) and 43 basic (NEPHGE)) that are present mainly in karyoplasts. One of these polypeptides (IEF 49) has previously been shown to be a polypeptide marker for cycling cells. A total of 59 polypeptides (27 acidic and 32 basic) were found to be present mainly in cytoplasts. Many polypeptides (109 acidic and 18 basic) including Y and beta-actin (60% in cytoplasts), beta-tubulin (60% in cytoplasts), vimentin (75% in cytoplasts) and alpha-actinin (65% in cytoplasts) were found to be present in both cellular fragments. These results could be of value in assigning the cellular distribution of potential regulatory proteins.

Demonstration of dissimilar acute haemodynamic effects of ethanol and acetaldehyde

To determine whether the acute cardiac depressant effects of ethanol could be attributed to its metabolite (acetaldehyde), either ethanol or acetaldehyde was intravenously infused into pentobarbital anaesthetised, closed-chest dogs. At a venous blood ethanol level of 199 +/- 43 (SE) mg . dl-1, ejection fraction had decreased from 35 +/- 2 to 30 +/-2%, P less than 0.05, max dP/dt/end-diastolic volume from 14.0 +/- 2.1 to 8.6 +/- 1.1 kPa . s-1 . cm-3 (105 +/- 16 to 65 +/- 8 mmHg . s-1 . cm-3), P less than 0.02, whereas end-diastolic volume (P less than 0.005), myocardial oxygen consumption (P less than 0.05) and coronary blood flow (P less than 0.005) had increased. Higher ethanol levels exaggerated these changes when peak arterial acetaldehyde was 20.2 +/- mumol . litre-1. By contrast, infusion of acetaldehyde to a peak blood level comparable with that produced by ethanol increased cardiac output from 2.4 +/- 0.2 to 2.8 +/- 0.2 litre-1 . min-1 P less than 0.01), coronary sinus oxygen saturation from 46 +/- 4 to 55 +/- 3% (P less than 0.25) and reduced systemic resistance from 8.0 +/- 0.7 to 6.3 +/- 0.5 kPa . litre-1 . min-1 (60 +/- 5 to 47 +/- 4 mmHg . litre-1 . min-1) (P less than 0.001). High dosage of acetaldehyde to a level of 129 +/- 23 mumol . litre-1 produced elevation of cardiac output (P less than 0.001), ejection fraction (P less than 0.01), coronary blood flow (P less than 0.02), whereas systemic resistance (P less than 0.001), heart rate (P less than 0.05) and myocardial oxygen consumption (P less than 0.05) decreased. Discontinuation of acetaldehyde infusion significantly reversed these changes. Max dP/dt/left ventricular end-diastolic volume and left ventricular end-diastolic volume were not significantly altered by acetaldehyde. Thus, ethanol depresses cardiac performance and increases myocardial oxygen consumption. By contrast, acetaldehyde at levels produced by ethanol metabolism improves cardiac performance, consequent to afterload reduction, and reduces myocardial oxygen consumption.