[Expression of sperm-specific glyceraldehyde-3-phosphate dehydrogenase in melanoma cells changes their energy metabolism]. / Ékspressiia spermospetsifichnoi glitseral'degid-3-fosfatdegidrogenazy v melanomnykh kletkakh izmeniaet ikh énergeticheskii obmen.

The somatic isoform of the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH; EC1.2.1.12) is involved in such crucial for cancer cells development pathways as induction of apoptosis and glycolytic regulation. At the same time, sperm-specific isoform (GAPDHS) does not exhibit all the same functions as somatic enzyme. The expression of sperm-specific GAPDH without N-terminal domain in some melanoma cells along with somatic isoenzyme, shown in our previous work, has led to the proposal of this unusual enzyme's possible role in regulation of cancer cells glycolysis. In the presented work we have tested production of GAPDHS in 13 additional melanoma cell lines by immunoblotting. We have also gathered data on energy metabolism in 5 selected cell lines by evaluation of glucose uptake and lactate production in differing conditions. We have demonstrated that in standard cultivation media glucose uptake by MelP cells, producing substantial amounts of GAPDHS protein was higher than in MelKor cells, producing lesser amounts of GAPDHS. All other analyzed cell lines that do not produce GAPDHS (MelMS, MelSi and Malme3M) had even a lower glucose uptake rate.

Detection of a mutation in the intron of Sperm-specific glyceraldehyde-3-phosphate dehydrogenase gene in patients with fibrous sheath dysplasia of the sperm flagellum.

The fibrous sheath is a unique cytoskeletal structure surrounding the axoneme and outer dense fibres of the sperm flagellum. Dysplasia of the fibrous sheath (DFS) is a defect of spermatozoa observed in severe asthenozoospermic patients and characterised by morphologically abnormal flagella with distorted fibrous sheaths. Sperm-specific glyceraldehyde-3-phosphate dehydrogenase (GAPDS) is a glycolytic enzyme that is tightly associated with the fibrous sheath of the sperm flagellum. The enzymatic activity of GAPDS was investigated in sperm samples of seven patients with DFS and compared to that of normal spermatozoa (n = 10). The difference in GAPDS activity in DFS and normal spermatozoa was statistically significant (0.19 ± 0.11 and 0.75 ± 0.11 µmol NADH per min per mg protein respectively). Immunochemical staining revealed irregular distribution of GAPDS in the flagellum of DFS spermatozoa. Other five samples with typical alterations in the fibrous sheath were assayed for mutations within human GAPDS gene. In all five cases, a replacement of guanine by adenine was revealed in the intron region between the sixth and the seventh exons of GAPDS. It is assumed that the deficiency in GAPDS observed in most DFS sperm samples is ascribable to a disorder in the regulation of GAPDS expression caused by the mutation in the intron region of GAPDS gene.

Dimerization of Tyr136Cys alpha-synuclein prevents amyloid transformation of wild type alpha-synuclein.

Expression of human alpha-synuclein in E. coli cells is known to result in a mixture of the wild type alpha-synuclein and the protein containing Tyr136Cys substitution due to the translational error. The amount of Cys136 alpha-synuclein (Cys136-AS) may reach approximately 50% of the recombinant protein. The wild-type and Cys136-containing fractions of alpha-synuclein were separated using thiol-Sepharose, and their properties were investigated. In the absence of reducing agents, Cys136-AS forms dimers due to the disulfide bonding. Both wild-type and Cys136 alpha-synuclein preparations are prone to aggregate during prolonged incubation under shaking at pH 4 and 37°C, but only the wild-type alpha-synuclein produces amyloid aggregates. The aggregates produced by either monomeric or dimeric Cys136-AS do not exhibit amyloid properties according to the test with Thioflavin T. Moreover, an admixture of dimeric Cys136-AS prevents the amyloid transformation of the wild-type alpha-synuclein. CD spectroscopy analysis revealed an enhanced content of alpha-helical structures in the aggregates produced by dimeric Cys136-AS. The admixture of Cys136-AS in preparations of human recombinant alpha-synuclein can be a source of erroneous interpretation of experiments on amyloid transformation of this protein.

Denaturing action of adjuvant affects specificity of polyclonal antibodies.

Influence of the immunization procedure on the specificity of the produced antibodies towards different conformations of the antigen was investigated. It was demonstrated that intravenous immunization of a rabbit with an adjuvant-free solution of recombinant sperm-specific glyceraldehyde-3-phosphate dehydrogenase (dN-GAPDS) resulted in production of antibodies recognizing only native conformation of dN-GAPDS and exhibiting no cross-reaction with somatic isoenzyme of glyceraldehyde-3-phosphate dehydrogenase. A subcutaneous immunization with human dN-GAPDS mixed with Freund's complete adjuvant yielded antibodies recognizing both native and denatured conformation of dN-GAPDS. The oil component of the adjuvant was shown to cause inactivation and partial denaturation of dN-GAPDS, leading to exposure of the epitopes that are masked in the native protein, which resulted in production of the antibodies to the denatured antigen. These results may be of importance for biochemical research that often require polyclonal antibodies recognizing different conformations of antigens.

Structural basis for the NAD binding cooperativity and catalytic characteristics of sperm-specific glyceraldehyde-3-phosphate dehydrogenase.

Catalytic properties of enzymes used in biotechnology can be improved by eliminating those regulatory mechanisms that are not absolutely required for their functioning. We exploited mammalian glyceraldehyde-3-phosphate dehydrogenase as a model protein and examined the structural basis of the NAD(+) cooperative binding exhibited by its homologous isoenzymes: the somatic enzyme (GAPD) and the recombinant sperm-specific enzyme (dN-GAPDS). Moreover, we obtained a mutant dN-GAPDS, which misses the cooperativity, but exhibits a twofold increase in the specific activity instead (92 and 45 µmol NADH/min per mg protein for the mutant and the wild type proteins, respectively). Such an effect was caused by the disruption of the interdomain salt bridge D311-H124, which is located close to the active site of the enzyme. The thermal stability of the mutant protein also increased compared to the wild type form (heat absorption peak values were 70.4 and 68.6 °C, respectively). We expect our findings to be of importance for the purposes of biotechnological applications.

Sperm-Specific Glyceraldehyde-3-Phosphate Dehydrogenase - An Evolutionary Acquisition of Mammals.

This review is focused on the mammalian sperm-specific glyceraldehyde-3-phosphate dehydrogenase (GAPDS). GAPDS plays the major role in the production of energy required for sperm cell movement and does not perform non-glycolytic functions that are characteristic of the somatic isoenzyme of glyceraldehyde-3-phosphate dehydrogenase. The GAPDS sequence is composed of 408 amino acid residues and includes an additional N-terminal region of 72 a.a. that binds the protein to the sperm tail cytoskeleton. GAPDS is present only in the sperm cells of mammals and lizards, possibly providing them with certain evolutionary advantages in reproduction. In this review, studies concerning the problems of GAPDS isolation, its catalytic properties, and its structural features are described in detail. GAPDS is much more stable compared to the somatic isoenzyme, perhaps due to the necessity of maintaining the enzyme function in the absence of protein expression. The site-directed mutagenesis approach revealed the two GAPDS-specific proline residues, as well as three salt bridges, which seem to be the basis of the increased stability of this protein. As distinct from the somatic isoenzyme, GAPDS exhibits positive cooperativity in binding of the coenzyme NAD+. The key role in transduction of structural changes induced by NAD+ is played by the salt bridge D311-H124. Disruption of this salt bridge cancels GAPDS cooperativity and twofold increases its enzymatic activity instead. The expression of GAPDS was detected in some melanoma cells as well. Its role in the development of certain pathologies, such as cancer and neurodegenerative diseases, is discussed.

Recombinant human sperm-specific glyceraldehyde-3-phosphate dehydrogenase: structural basis for enhanced stability.

Sperm-specific glyceraldehyde-3-phosphate dehydrogenase (GAPDS) is bound to the fibrous sheath of the sperm flagellum through the hydrophobic N-terminal domain of the enzyme molecule. Expression of human GAPDS in E.coli cells yields inactive and insoluble protein. Presumably, the N-terminal domain prevents correct folding of the full-length recombinant enzyme. To obtain GAPDS in a soluble and active form, a recombinant enzyme lacking in 68 amino acids of the N-terminal domain (dN-GAPDS) was expressed in E.coli cells. Purified dN-GAPDS was shown to be a protein of 9.3 nm in diameter (by dynamic light scattering), which is close to the size of the muscle tetrameric glyceraldehyde-3-phosphate dehydrogenase (8.6 nm). The catalytic properties of the protein differed a little from those of the muscle glyceraldehyde-3-phoshate dehydrogenase. However, compared to muscle glyceraldehyde-3-phoshate dehydrogenase, dN-GAPDS exhibited enhanced thermostability (the transition midpoints values are 60.8 and 67.4°C, respectively) and was much more resistant towards action of guanidine hydrochloride (inactivation constants are 2.45±0.018 and 0.118 ± 0.008 min(-1), respectively). The enhanced stability of dN-GAPDS is likely to be related to some specific features of the GAPDS structure compared to that of the muscle enzyme: 1) reduced number of solvent-exposed salt bridges; 2) 2 additional buried salt bridges; and 3) 6 additional proline residues in GAPDS meeting the "proline rule". It is assumed that high stability of the sperm-specific GAPDS is of importance for the efficiency of fertilization.

Investigation of glyceraldehyde-3-phosphate dehydrogenase from human sperms.

Glyceraldehyde-3-phosphate dehydrogenase (GAPDs) was purified from human sperms and properties of the enzyme were investigated. After sonication of sperms, the most part of GAPDs is associated with the insoluble cell fraction. Trypsin treatment results in the cleavage of part of the N-terminal domain of the enzyme yielding a soluble fragment that was purified by hydrophobic chromatography on Phenyl-Sepharose. The isolated fragment was shown to be a tetramer with molecular weight of approximately 150 kD (according to Blue Native PAGE) and composed of subunits of 40 kD (according to SDS-PAGE). The specific activity of the isolated fragment reached 374 U/mg. It is supposed that GAPDs exists in sperms as the tetrameric molecule bound to the fibrous sheath of the flagellum through the N-terminus of one or two subunits. Comparative study of the amino acid sequences of mammalian GAPDs revealed conservative cysteine residues (C21, C94, and C150) that are specific for the sperm isoenzyme and absent in the somatic isoenzyme. Residue C21 can be involved in the formation of the disulfide bond between the N-terminal domain of GAPDs and fibrous sheath proteins.

Somatic and sperm-specific isoenzymes of glyceraldehyde-3-phosphate dehydrogenase: comparative analysis of primary structures and functional features.

The elucidation of the interdependence between structural features and functions of somatic and sperm-specific isoenzymes of glyceraldehyde-3-phosphate dehydrogenase (GAPD and GAPDS, respectively) was the goal of comparative analysis of their primary structures. GAPDS was shown to lack the sequence similar to the atypical nuclear export signal motif (NES) of the somatic isoenzyme GAPD. This finding is confirmed by experimental data on the absence of interaction between GAPDS and antibodies 6C5 recognizing the NES motif in the sequence of GAPD. The lack of NES correlates with functional peculiarities of the sperm-specific enzyme that is tightly bound to the fibrous sheath of the sperm flagellum. The sequences of the two isoenzymes were examined for the short motifs that might participate in apoptosis, endocytosis, and DNA repair. Sites of phosphorylation by different protein kinases have been revealed in both isoenzymes, and their characteristic features are discussed. These observations can serve as the basis for subsequent search for new ways of regulating the two isoenzymes.