Effects of conditioning polarization on the membrane ionic currents in rat myometrium

The regulatory function of mixed lineage kinase 3 in tumor and host immunity

Protein kinases are the second most sought-after G-protein coupled receptors as drug targets because of their overexpression, mutations, and dysregulated catalytic activities in various pathological conditions. Till 2019, 48 protein kinase inhibitors have received FDA approval for the treatment of multiple illnesses, of which the majority of them are indicated for different malignancies. One of the attractive sub-group of protein kinases that has attracted attention for drug development is the family members of MAPKs that are recognized to play significant roles in different cancers. Several inhibitors have been developed against various MAPK members; however, none of them as monotherapy has shown sustainable efficacy. One of the MAPK members, called Mixed Lineage Kinase 3 (MLK3), has attracted considerable attention due to its role in inflammation and neurodegenerative diseases; however, its role in cancer is an emerging area that needs more investigation. Recent advances have shown that MLK3 plays a role in cancer cell survival, migration, drug resistance, cell death, and tumor immunity. This review describes how MLK3 regulates different MAPK pathways, cancer cell growth and survival, apoptosis, and host's immunity. We also discuss how MLK3 inhibitors can potentially be used along with immunotherapy for different malignancies.

Inactivation of calcium channel current in rat uterine smooth muscle: evidence for calcium- and voltage-mediated mechanisms

Ca channel currents were recorded in Cs-loaded myometrial strips from pregnant rats after addition of tetraethylammonium chloride and 4-aminopyridine (10 mM each) by means of a double sucrose-gap technique. During a depolarizing pulse, the decay of Ca channel current was slowed down when external Ca was replaced by Ba or Sr. This decay represented an inactivation phenomenon, as assessed by the decreased amplitude of inward tail currents following progressively longer depolarizations, the absence of shift in peak conductance curves against membrane potential, and the stable value of the reversal potential when Ba current was increased during conditioning pulses. Inactivation of Ca and Ba currents through Ca channels was studied using the double-pulse method. Conditioning pulses that produced maximal Ca current induced maximal inactivation; with stronger depolarizations, inactivation decreased but was not completely prevented at the expected Ca reversal potential. Increasing the amount of Ca entering the cell during the pre-pulse reduced both amplitude and kinetics of test Ca currents. These results were not observed with Ba as charge carrier suggesting the participation of different mechanisms in inactivation. With Ca as charge carrier, increasing the external Ca speeded the rate of inactivation. This was not observed with Ba outside. Addition of Co (2.5 mM) reduced the amplitude of both Ca and Ba currents but slowed the inactivation of only the Ca current. Recovery from inactivation was described as a two-exponential process only when the conditioning pulse elicited a Ca inward current. In all other cases, recovery from inactivation was represented as a single exponential curve. It is suggested that inactivation of Ca channels in rat uterine smooth muscle is mediated by both internal Ca-dependent and potential-dependent mechanisms.

Effects of goniopora toxin on non-adrenergic, non-cholinergic response and purine nucleotide release in guinea-pig taenia coli

1. Effects of goniopora toxin (GPT) on non-adrenergic, non-cholinergic inhibitory responses were examined in isolated guinea-pig taenia coli and the transmission mechanism was analysed.2. GPT (20-50 nM) gradually augmented the relaxation and rebound contraction induced by electrical transmural stimulation in the presence of guanethidine and atropine. These effects were abolished by tetrodotoxin.3. The resting tension and the response to exogenously applied ATP were little affected by GPT.4. The action potentials and the electrotonic potentials recorded by a double sucrose-gap method were little affected by GPT.5. These results indicate that the augmentation is elicited by a direct action of GPT on the non-adrenergic, non-cholinergic neurones, rather than on the smooth muscles per se.6. GPT augmented the amplitude of the inhibitory junction potential (i.j.p.) recorded in the presence of guanethidine and atropine. GPT also enhanced the (3)H efflux in response to electrical transmural stimulation of preparations pre-loaded with [(3)H] adenosine. Tetrodotoxin markedly inhibited or abolished the i.j.p. and (3)H efflux.7. These results would suggest that augmentation of the non-adrenergic, non-cholinergic responses is due to increased transmitter release from the nerve. Under conditions in which the transmitter release was augmented, the non-adrenergic, non-cholinergic response showed an essentially similar pattern to that obtained under normal conditions; therefore the inhibitory response is probably due to a putative transmitter, possibly ATP or a related nucleotide.