Technology

Article Review special type of writing that involves reading an article and then providing the reader with your personal take on its content

Introduction
Porins are special type of proteins which are embedded in biological membranes in order to function for a better facilitated transfer of particles through the specific membrane of interest. Aquaporins, on the other hand, are a family of more specialized membrane proteins found in bacteria, plants, and animals which serve two particular roles in the maintenance of internal physiological equilibrium. The first of these roles is described in the event of rapid transmembrane transport of water as driven by osmotic gradients. In this case, aquaporins help defy the effects pressure gradients on the transfer of substances from an area of low particle concentration to an area of high particle concentration. The second role of aquaporins is the conduction of ion currents through the membrane. Consequently, both of the mentioned roles of aquaporins are possessed by aquaporin1 or AQP1, found in endothelial cells, red blood cells, renal proximal tubule cells, and choroid plexus epithelium. However, the importance of AQP1 is most notable during peritoneal dialysis, angiogenesis, and endothelial permeability. With this mind, researchers believe that the regulation of AQP1 is a vital aspect of the maintenance of the aforementioned physiological processes. Unfortunately, little is known about the regulatory mechanism of AQP1 because it was originally perceived to be constitutively open. Hence, the study by Zhang and associates was designed to investigate the regulatory mechanism of AQP1 in relation to protein kinase C (PKC) activities.

Body
In order to carry out the goal of the study, the researchers made use of Xenopus laevis oocytes to observe the normal functioning of AQP1 in a wild type state. Laboratory procedures such as the hypotonic swelling experiment and subsequent current estimates of the channel were performed. With respect to the ability to increase water permeability, it was discovered that the use of OAG, the physiological activator of the PKC, corresponds to subsequent increase in volume of the PKC activated cells and such kind of activity is indicative of the increased permeability of the channel to water components. Regulation of PKC channels, on the other hand, was found to be dependent on the availability of Thr157 and Thr239 sites. The threonine (Thr) sites were inactivated by replacing the threonine residue with alanine and it was discovered that such kind of mutagenesis leads to the removal of the positive regulation of AQP1 water permeability by PKC.

After the investigation of the participation of protein kinase C to water permeability, the researchers then investigated its effect on ion conductance by subjecting the Xenopus oocytes to electrophysiological experiments. In this case, a different PKC activator was used, PMA. Results showed that current amplitudes increased by 102.5 - 4.1. Moreover, the effects of threonine site inactivation were also tested for ion conductance and it was discovered that attenuation of one of the two sites resulted in low ion current transmission across the AQP1 mediated channel. After these experiments, the researchers tried to investigate if the protein kinase C pathway is related to the previously suspected AQP1 regulatory pathway, the cyclic nucleotide-induced activation. Results showed that the use of cGMP in cyclic nucleotide activation of AQP1 also leads to improved water permeability and ion transmission processes, but the results were significantly independent to that of the PKC pathway.  

Conclusion
The experimental procedures in this study were done to investigate the participation of the PKC regulatory pathway on the activity of AQP1 in Xenopus oocytes. It was observed that all results affirm to the positive regulation of PKC to both water permeability and electrical current transmission. These findings can be practically applied in the modulation of endothelial permeability, angiogenesis, and urine concentration. This is because of the fact that the mentioned processes are previously determined to be affected by the proper functioning of PKC which is identified to be a regulator of AQP1. In like manner, protein kinase C participation in AQP1 channels was also seen to be present in choriod plexus epithelium. Consequently, this event shows that the central nervous pathway and the PKC pathway are two mechanisms which can significantly increase water permeability and ion conductance.

In general, this study provides firsthand information on the application of protein kinase C in aquaporin1. Through empirically administered methods, the researchers found out that PKC positively regulates the water permeability and ion conductance of AQP1. Furthermore, it was discovered that the threonine sites Thr157  Thr239 of the enzyme are directly involved in the regulation process. Employment of mutation on the two amino acid sites correspond to a decrease or inactivation of the positive regulatory mechanisms. It was also found in this study that the PKC pathway is independent of the cyclic nucleotide pathway which means that the PKC pathway can be solely used to monitor and regulate specific endothelial processes, blood vessel differentiation and formation, and the formulation of alternative ways of addressing urinary dialysis methods. Lastly, research of this type must continually be done in order to increase current knowledge on various regulatory mechanisms and to be able to offer novel ways in solving physiological medical concerns of humans, plants and animals.