Search PubMed⌕ Search

Biomedical subjects

J V Kozlov

Publications and source records attributed to J V Kozlov.

9 recordsLinked to original sources
PubMed2001

Ricin.

The plant toxin ricin consists of two disulfide-linked polypeptides with different functions. The A-chain enters the cytosol and inactivates the ribosomes enzymatically, whereas the B-chain has lectin properties and binds to carbohydrates at the cell surface. This binding is a requirement for translocation of the A-chain to the cytosol. The bound toxin is endocytosed and transported retrograde through the Golgi apparatus to the endoplasmic reticulum where it appears to be translocated to the cytosol by the sec61p complex.

Animals↗
PubMed1995

Role of processing and intracellular transport for optimal toxicity of Shiga toxin and toxin mutants.

Cleavage of Shiga toxin A-fragment at a highly trypsin-sensitive site increases its enzymatic activity. To investigate the role of this cleavage site in intoxication of cells, we studied the routing, cleavage, and toxicity of mutant toxin where the trypsin-sensitive site had been eliminated. Ultrastructural analysis of toxin tagged with horseradish peroxidase demonstrated that wild-type and mutant toxins were transported from endosomes to the trans-Golgi network and further through the Golgi cisterns to the endoplasmic reticulum. Wild-type toxin was much more efficient than the mutants in provoking rapid intoxication, but after prolonged incubation time also mutants were highly toxic. The cells were able to cleave both wild-type Shiga toxin and the mutants, but the cellular location for cleavage appears to differ. Wild-type toxin was cleaved in the presence of brefeldin A, which disrupts the Golgi cisterns. This indicates that the cleavage occurs in the endosomes or in the trans-Golgi network. In contrast, the mutant Shiga-His (R248H/R251H) was not cleaved in the presence of brefeldin A, indicating that the cleavage can occur only after the toxin has left the trans-Golgi network. In vitro experiments showed that the cytosolic enzyme calpain is able to cleave Shiga-His, and results from in vivo experiments are consistent with the possibility that cleavage is carried out by calpain after the mutant A-fragment has reached the cytosol.

Amino Acid Sequence↗
PubMed1993

Entry of Shiga toxin into cells.

The effect of Shiga toxin with mutations in the A fragment has been tested on cells in order to get more information about the processing of the A fragment during entry into the cytosol. A mutant with a deletion between the A1 and A2 domain in the A fragment is resistant to cleavage by trypsin and is less toxic than wild type toxin on both Vero and A431 cells. The results support the view that processing of the A fragment is important for the high toxicity of the wild type toxin. A number of cell lines are resistant to Shiga toxin although they bind the toxin. However, A431 cells can be sensitized by butyric acid treatment, and transport of Shiga toxin to the Golgi apparatus seems to be required for the intoxication in the sensitized cells. The role of retrograde transport through the Golgi apparatus to the endoplasmic reticulum (ER) will be discussed.

Amino Acid Sequence↗
PubMed1992

Retrograde transport of endocytosed Shiga toxin to the endoplasmic reticulum.

Shiga toxin and some other protein toxins that act on targets in the cytosol have previously been shown to enter the trans-Golgi network. Transport by this route may be necessary for translocation of the toxin to the cytosol and for intoxication, but it is not known whether the enzymatically active part of the toxins actually enters the cytosol from the trans-Golgi network. It has been suggested that such toxins are transported in a retrograde manner to the endoplasmic reticulum and that translocation occurs in this organelle, but retrograde transport of endocytosed material beyond the trans-Golgi network has never been demonstrated. Here we show that in butyric acid-treated A431 cells endocytosed Shiga toxin is not only transported to the trans-Golgi network, but also to all Golgi stacks, to the endoplasmic reticulum and to the nuclear envelope. Furthermore, butyric acid sensitizes the cells to Shiga toxin, which is consistent with the possibility that retrograde transport is required for translocation of the toxin to the cytosol.

Bacterial Proteins↗
PubMed1991

Bacterial protein toxins acting on intracellular targets.

A number of bacterial toxins act on targets located in the cytosol. Diphtheria toxin, Pseudomonas aeruginosa exotoxin A and shigella toxin inhibit protein synthesis by enzymatic inactivation of elongation factor 2 or the 60 S ribosomal subunit. These toxins enter the cells by receptor-mediated endocytosis, followed by translocation across the membranes of intracellular organelles. Also a number or toxins that are not cytocidal act on targets in the cytosol. A number of nontoxic bacterial proteins are able to modify enzymatically intracellular molecules. Some of these proteins could be considered for targeting to special cells followed by translocation to obtain defined physiological effects.

ADP Ribose Transferases↗
PubMed1981

On the origin of the H1N1 (A/USSR/90/77) influenza virus.

The influenza virus H1N1 (the A/USSR/90/77 strain) that reappeared in 1977 after the H1N1 influenza viruses had disappeared from the human population, is compared with the A/FM/1/47 and the A/FW/1/50 influenza viruses by the method of oligonucleotide mapping of individual segments of the viral RNAs. Seven genes of the A/USSR/90/77 virus appear to be very similar to the corresponding genes of the A/FW/1/50 virus, whereas the gene coding for the M protein displays considerable homology to the corresponding gene of the A/FM/1/47 virus. The data demonstrate that the A/USSR/90/77 strain is a recombinant virus.

Genes, Viral↗