Abstract The role of vacuolar H+-ATPase (V-ATPase) in exocytic and endocytic membrane transport processes was studied by using its specific inhibitor, bafilomycin A1 (Baf A1), as a tool. On the exocytic pathway, both brefeldin A- and nocodazole-induced retrograde transport of Golgi proteins to the endoplasmic reticulum (ER) were inhibited by Baf A1. Furthermore, p58/ERGIC-53, which normally cycles between the ER, the intermediate compartment (IC), and cis-Golgi, was arrested in pre-Golgi tubules and vacuoles, and the number of p58-positive 80-nm Golgi (COPI) vesicles was reduced, suggesting that the drug inhibits the vesicle-mediated retrieval of the protein from post-ER compartments. The small GTPase rab1p was efficiently recruited to the tubules, accumulating in the presence of Baf A1. In contrast, these tubules showed no enrichment of anterogradely transported proteins, indicating that they participate in retrograde transport. Interestingly, acidic lumenal pH could only be detected in the more central pre-Golgi elements. The forward (anterograde) transport of newly synthesized Semliki Forest virus (SFV) and vesicular stomatitis virus (VSV) glycoproteins from the ER to the cis-Golgi was largely unaffected by Baf A1. However, maturation processes occurring in the trans-Golgi were inhibited, and the amounts of viral glycoproteins appearing at the cell surface were reduced. Newly synthesized VSV glycoprotein accumulated into rab1p-positive Golgi membranes in the presence of Baf A1, indicating that the transport from cis-Golgi was affected. Furthermore, O-glycosylation of the expressed CD8 chimeras and lectin cytochemistry experiments indicate that Baf A1 affects the transport from cis-Golgi. Instead, Baf A1 did not affect the transport of viral glycoproteins from the trans-Golgi network to the cell surface. We propose, that anterograde intra-Golgi traffic may be affected indirectly by Baf A1, as it inhibits retrograde vesicle-mediated transport and thus cisternal maturation. Baf A1 inhibited the entry of SFV into BHK-21 cells. Thus, V-ATPase was responsible for the acidification of the endosomes needed for virus entry. In cells infected with VSV and subsequently treated with Baf A1, virus particles were found to be accumulated in tubular membrane structures, which also contained endocytosed BSA-gold. Neither VSV nor BSA-gold particles were detected in lysosomal glycoprotein (lgp) 120-positive lysosomes, however. Thus, secreted and further endocytosed virus particles accumulate into tubulated endocytic organelles, apparently early endosomes, in Baf A1-treated cells. We conclude that the transport from endosomes to lysosomes is inhibited by Baf A1. The bulk of rab7 GTPase, which participates in vesicle fusion to late endosomes, was localized to the ruffled border (RB) membrane of bone-resorbing osteoclast. This indicates that the membrane has some characteristics of late endosomal membranes and that endocytic membrane transport is oriented towards the RB. Consistently, both endocytosed lumenal horseradish peroxidase and receptor-bound transferrin were delivered to the RB. The delivery of membrane-associated transferrin to the RB further indicates that the RB has some endosomal characteristics and suggests that the endocytic pathway contributes to the maintenance of functional RB. The endocytic pathway could act in balancing the membrane traffic associated with transcytosis from the RB to the basal plasma membrane. Endocytic processes in osteoclasts appeared to be very sensitive to Baf A1. Thus, blocking of the endocytic membrane traffic towards the RB could explain the inactivation of cells by low concentrations of the drug.

Glutamate is the main excitatory neurotransmitter in the CNS and at the neuromuscular junctions (NMJs) of invertebrate. The characteristic similarities to CNS glutamatergic synapses in vertebrate and the anatomical simplicity of invertebrate NMJs favor the investigation of glutamatergic synaptic functions in this system. This dissertation mainly aimed to physiologically separate two functional vesicle groups, the reserve pool (RP) and readily releasable pool (RRP) within presynaptic nerve terminals of Procambarus Clarkii and Drosophila melanogaster. This was addressed in part by blocking the vesicular glutamate transporter (VGlut) with bafilomycin A1. Various frequencies of motor nerve stimulation, exposure time, and concentration of bafilomycin A1 were examined. The low-output tonic opener NMJs in crayfish exposed to 4μM bafilomycin A1 and 20Hz continuous stimulation decreased the EPSP amplitude to 50% in ∼30min with controls lasting 3h. After activity and bafilomycin A1-induced synaptic depression, the EPSPs were rapidly revitalized by serotonin (5-HT, 1μM) in the crayfish preparations. The 5-HT action can be blocked almost completely with a PLC inhibitor, but partially with a cAMP activator. The higher output synapses of the larval Drosophila NMJ when stimulated at 1Hz or 5Hz and exposed to 4μM of bafilomycin A1 showed a depression rate of 50% within ∼10min with controls lasting ∼40min. After low frequency depression and/or exposure to bafilomycin A1 a burst of higher frequency (10Hz) can recruit vesicles from the RP to the RRP. Physiological differences in low- (tonic like) and high-output (phasic like) synapses match many of the expected anatomical features of these terminals, part of this dissertation highlights physiological differences and differential modulation and/or extent of the vesicles in a RP for maintaining synaptic output during evoked depression of the RRP in crayfish abdomen extensor preparation. With the use of bafilomycin A1, the tonic terminal is fatigue resistant due to a large RRP, whereas the phasic depresses rapidly upon continuous stimulation. Upon depression of the tonic terminal, 5-HT has a large RP to act on to recruit vesicles to the RRP; whereas, the phasic terminal, 5-HT can recruit RP vesicles to the RRP prior to synaptic depression but not after depression.

Type 2 diabetes mellitus represents a metabolic disease reaching epidemic dimensions in the 21st century. Fatty acid-induced apoptosis of pancreatic β-cells significantly contributes to its pathogenesis. Saturated fatty acids (FAs) are strongly cytotoxic for β-cells, whereas unsaturated FAs are well tolerable by β-cells, they are even able to inhibit proapoptotic effects of saturated FAs when co-incubated. According to recent studies, FAs-induced apoptosis in pancreatic β-cells is partly regulated by autophagy, a catabolic process involved in the degradation and recyclation of cell components in lysosomes. The aim of this diploma thesis was to contribute to the clarification of the role of autophagy in FAs-induced apoptosis regulation. We induced apoptosis in human pancreatic β- cell line NES2Y by 1 mM stearic acid (SA) and inhibited it with 0.2 mM oleic acid (OA) co- incubated with SA. We revealed, that the saturated SA used in apoptosis-inducing concentration simultaneously inhibits the autophagic flux in pancreatic NES2Y cell line. When SA is co- incubated with unsaturated OA in concentration sufficient for inhibition of proapoptotic effect of SA, OA is also able to inhibit the block of autophagy induced by the effect of SA. Application of unsaturated OA alone in this concentration did not...

Safety concerns arising from cytotoxic behavior of nanoparticles (NPs) in complex biological environment remain the main problem limiting NPs application in biomedicine. In this study, we have investigated cytotoxicity of NPs with different composition, shape and size, namely SiO2 NPs (SiNPs, 7-14 nm), superparamagnetic iron oxide NPs (SPIONs, 8 nm) and carboxylated multiwalled carbon nanotubes (CNTCOOHs, diameter: 60-100 nm, length: 1-2 μm). Cytotoxicity was evaluated with newly designed screening assay capable to simultaneously assess activity of cell dehydrogenases, activity of lactate dehydrogenase (LDH) released from cells into environment and number of intact cell nuclei and apoptotic bodies in human umbilical vein endothelial cell (HUVEC) culture growing in the very same well of the 96-well plate. Aforementioned attributes were subsequently utilized to obtain information about cell viability and necrotic and apoptotic aspects of cell death. Results from this "three-in-one" cell death screening (CDS) assay showed that SiNPs and CNTCOOHs evoked pronounced cytotoxic effect demonstrated as decrease of cell viability and development of apoptotic bodies formation. In contrast to this, SPIONs induced only mild cytotoxicity. Moreover, SiNPs impaired cell membrane leading to increased LDH release...