Том 12, № 1 (2018)

Septins, the cytoskeletal proteins discovered in the 1970s in budding yeast cells, are currently detected in most postmitotic cells of animals and humans. In the last decade, significant progress has been made in understanding the biochemical properties of septins and their biological functions. An increasing number of studies show that these proteins play an important role in the development and physiology of specific tissues and organs. The review surveys classification, major functions and localization of septins in the nervous system of mammals and humans. Models describing the mechanisms of the septin involvement in the neurotransmitter secretion from nerve endings and the role of septins in the pathogenesis of various neurodegenerative diseases are discussed.

The electrical polarization of the inner mitochondrial membrane largely determines the electrochemical potential of hydrogen ifons, being thereby a significant factor in the energy transformation during oxidation of respiratory substrates and its accumulation in the form of newly synthesized ATP. However, the gradient of the electric potential on the inner mitochondrial membrane (ΔΨm) performs a number of functions not related to energy production. Even under hypoxic conditions, precluding the formation of ATP in mitochondria through oxidative phosphorylation, mitochondria maintain their ΔΨm at the expense of the hydrolysis of cellular ATP, which indicates the exceptional importance of ΔΨm for non-energetic functions of mitochondria. Among these functions, the mitochondrial inward transport of metal cations and proteins carrying a positively charged amino acid sequence and export of anions including nucleic acids possibly providing retrograde signaling, seem very important and essential for maintaining mitochondrial structure and metabolism. ΔΨm is a powerful regulator of mitochondrial generation of reactive oxygen species that perform physiological and pathological functions. And finally, ΔΨm is a critical element in the mechanism of disposal of dysfunctional mitochondria, the so-called quality control machinery of mitochondria. The disturbance of this mechanism leads to increase of heterogeneity in the population of mitochondria in the cell, and the degree of heterogeneity can be considered as an indicator of the pathological cellular phenotype. Correlation between Ψm and cell functions is difficult to identify without adequate quantitative estimates of the magnitude of ΔΨm, which are complicated due to several cellular and mitochondrial processes that affect the experimentally obtained values. Recommendations for assessing the contribution of these processes and avoiding artifacts in the measurements of ΔΨm by standard methods are given.

The negative regulation of expression of genes involved in various metabolic pathways in a skeletal muscle is the main function of histone deacetylases 4 and 5 (HDAC4/HDAC5). HDAC4 and HDAC5 seem to be the targets of the AMP-activated protein kinase (AMPK). Earlier, an essential decrease in the level of Thr172-phosphorylated-AMPK in a rat soleus muscle at the first day of gravitational unloading was shown. Possibility of a protein kinase D (PKD) to phosphorylate histone deacetylases 4/5 has been shown, too. We supposed that under the conditions of gravitational unloading, alterations in AMPK phosphorylation level can affect regulation of nuclear-cytoplasmic traffic of class II histone deacetylases and of various skeletal muscle genes expression. To verify the hypothesis, we used administration of an AMPK activator, AICAR, before and during a day-long hindlimb suspension. It was shown that at an early stage of gravitational unloading, HDAC4 is not a PKD target, and its nuclear import is realized due to decrease in AMPK activity. We were the first to show reciprocal relations between AMPK and PKD in a skeletal muscle at early gravitational unloading.

The radical-producing activity of human platelets has been studied using the enhanced chemiluminescence method. It is shown that chemiluminescence of isolated platelets is observed only in the presence of lucigenin, a selective probe for superoxide anion; the luminescence is amplified many times upon the addition of NADH and NADPH, the substrates of oxidative chains. The chemiluminescence is not affected by diphenyliodonium, an inhibitor of NADPH oxidase, but it is inhibited in a dose-dependent manner by the oxidative phosphorylation uncouplers dinitrophenol and rotenone. Thus, a superoxide anion radical is the main free radical generated by platelets, and mitochondria are one of the superoxide anion radical sources in platelets.

Pannexin 1 (Panx1) forms plasma membrane channels that release ATP, an important vascular tone regulator. However, despite the abundant expression of Panx1 in the vascular system, its effects on smooth muscle contraction are not evident in all arteries. In this study, we tested the hypothesis that the functional consequences of Panx1 deficiency can be masked by the augmented action of ATP secreted in a Panx1-independent way. Experiments were performed on small mesenteric arteries obtained from Panx1-knockout (Panx1^–/–) and C57Bl/6 (Panx1^+/+) male mice using wire myography of endothelium-denuded arterial preparations and reverse-transcription quantitative PCR techniques. Arterial contractile responses to phenylephrine did not differ in two experimental groups. Ecto-ATPase inhibitor ARL67156 (100 μM) potentiated the responses to phenylephrine in Panx1^+/+ but not in Panx1^–/–, while ARL67156 did not affect the contractile responses to the thromboxane A2 receptor agonist in any of the two groups. Contractile responses to exogenous ATP (10 μM) were smaller in Panx1^+/+ than in Panx1^–/– mice. By contrast, NTPDase1 mRNA content was higher in Panx1^+/+ than in Panx1^–/– mice. These results suggest that ATP released from smooth muscle cells through Panx1 channels can potentiate contractile responses of murine mesenteric arteries upon activation of α₁-adrenoceptors. In Panx1^–/– mice an increased arterial ATP sensitivity and diminished NTPDase1 activity may augment the contractile effects of Panx1-independent ATP.

Disturbances in cerebral blood flow cause hypoxic and ischemic processes that lead to damaging and death of neurons. Some populations of GABAergic neurons are characterized by greater sensitivity to oxygen-glucose deprivation. Massive damage and death of the cells (more than 80%) take place in hippocampal cultures during long oxygen-glucose deprivation (40 min). Astrocytes and GABAergic neurons are destroyed first, which in turn leads to the neuroglial network disturbances accompanied by massive death of glutamatergic neurons. In the present work we investigated a protective role of calcium-binding proteins (CaBPs) in the population of GABAergic neurons under hypoxic-like and ischemic-like conditions. The preconditioning was evaluated by suppression of the NMDAR activity after short-term episodes of hypoxia. The posthypoxic hyperexcitability was estimated by the appearance of synchronous spontaneous calcium impulses (s[Ca²⁺]_i) at the reoxigenation stage. The cells damaged during hypoxia and ischemia were detected by the presence of the irreversible increase of [Ca²⁺]_i. The type of neurons and presence of CaBPs (parvalbumin (PV), calbindin (CB), calretinin (CR)) were determined by immunohistochemistry after registration of the [Ca²⁺]_i dynamics. We have shown that any calcium-binding protein in GABAergic neurons can play the role of an endogenous neuroprotector, which prevents calcium overload and subsequent death even without preconditioning. GABAergic neurons containing any CaBP are characterized by lower magnitudes of the calcium responses to the NMDA application. These neurons are not preconditioned by repeated short-term episodes of hypoxia. It was shown that GABAergic neurons containing CR are characterized by the absence of irreversible calcium increases and survive during oxygen-glucose deprivation. However, the presence of PV or CB can lead to the appearance of lag phases with different durations. These two CaBPs reduce the rate of calcium increase and possibly in that way prevent the death of GABAergic neurons under the ischemia-like conditions.