Gene Expression and Signaling Class
Short Answer
Different Phenotype in PTEN Mutations
While PTEN is either mutated or lost in both spontaneous and heritable cancers, the p110 alpha is frequently mutated in major forms of cancer such as breast cancer, endometrial, colorectal, ovarian, and prostate cancers with a greater prevalence of breast cancers (Nagata et al., 2004). Besides, the monoallelic loss of PTEN mostly contributes to the growth of tumor in the context of other somatic mutations in which case the count of PTEN proteins correlates with the severity of cancer, an indication that PTEN is haploinsufficient in functionality. Additionally, while the gene encodes p110 alpha, the catalytic subunit of p13k has mutations in similar cancers as PTEN but cluster in two regions of the gene in the head and neck.
Growth Factor Activation of PI3K
The activity of PI3K determines regulation of most cellular functions. The products of PI3K activity include motility, viability, proliferation, and vesicle transport. The PI3K molecules responsible for the production of these products form a large enzyme family. The catalytic activity of this family regarding vitro and sequence alignment forms the basis of their division into three classes. The class 1 of this family acts as a mediator of receptor signaling which forms the basis of the statement that growth factor activation of PI3K results from recruitment of the enzyme to the activated receptor (Hennessy et al., 2005). Besides, following stimulation of the epidermal growth factor receptor, some class II PI3Ks are recruited into a phosphotyrosine that contains a signaling complex.
The Class III enzymes are expressed mostly in the retina where they counter the accumulation of misfolded proteins damaged oxidatively. On the other hand, the Class I enzymes are only present in cases where oxidoreduction reactions occur with oxygen as the receptor being referred to as oxidase while reductase is a generally accepted alternative name for the enzymes (Mirza et al., 2010). These enzymes are rare in the cells as compared to class III enzymes, which appear in the retina mostly in higher numbers and subclasses. Their products have a similar pattern like the enzymes where they appear in large quantities in cases of class III enzymes. However, they are few in the cases where class I enzymes are concerned.
Specificity of PH Domains
PH domains, best known for their high affinity and specificity in binding onto phosphoinositides, are among the commonest type of domains. However, only less than 10% of all known PH domains share in this property with most cases that share in this property involving phosphoinositides that have on their inositol head group a pair of adjacent phosphates that allow for easy binding between the PH domains and the phosphoinositides (Toker & Marmiroli 2014). While the other 90% still do bind to phosphoinositides, the affinity is too weak suggesting likely functional irrelevance except for one group that has since been confirmed to bind to both phosphoinositides and ARF family both of which are located in the Golgi apparatus. However, in this case, the PH domains only merely act as coincidence detectors.
AKT and mTORC Relations
The PI3K, AKT, and mTORC are a survival pathway constituted in many cancers to form the basis for regulation of cellular growth thus containing cancer (Hennessy et al., 2005). The pathway is activated through several mechanisms including suppression of the PTEN, amplification or mutation of PI3K and AKT, activation of growth factor receptors, as well as the exposure to carcinogens mostly used in cancer treatment. Upon activation of the pathway, signaling through the AKT allows for propagation to several arrays of substrates that include the mTORC which serves as a key regulator of the translation of proteins. The pathway acts as a convergence point for many growth stimuli in cancer patients, which makes it an attractive target for the treatment of cancer. Besides, activation of the pathway confers resistance to many cases of cancer therapy that makes it a poor prognostic factor in the disease treatment. In essence, the treatment of cancer mostly plays around the invention of inhibitors to this pathway.
E542K and E545K in the Helical Domain
I hypothesize that the helical domains house the AKT/PI3K/mTORC pathway where prolific growth in cancer patients happens. The mutants E542K and E545K cause the prolific growth of tumors caused by an activation of the pathway described above (Hennessy et al., 2005). A possible test to confirm this postulation would be the application of inhibitors that limit the cellular function of these mutants around the helical domains of a cancer patient and a non-cancer patient. The examination can be evaluated by examining the effects of binding p85 by abolishing the binding of alpha human p110 to p85 via the partial or total deletion of the alpha p110. The results of these two tests can then be compared in order to relay their differences. It would be expected that the inhibitors around the helical domain will show positive results where cancerous growth stops in an affected patient due to their inhibitory effect on the mutants. Using a differential interaction method where the E542K and E545K are varied to measure the mutation effects from the resulting cells, the mutations and hypothesis stated above can be evaluated. If the manipulations of the E542K and E545K lead to increase mutations that would cause cancer, then the hypotheses that AKT/PI3K/mTORC pathway housed by helical domains leading to mutations is valid.
PI3K Kinase Signaling
The tests carried out will need to revolve around the ‘messagers’ relationship to PI3K, which affects the target pathway to the tumor growth upon activation of the pathway (Hennessy et al., 2005). These will include testing for the PTEN, mTORC, and the various AKT proteins such as AKT1, AKT2, and AKT3. There are various mechanisms of signal transduction cascade that explain the protein expression. These are the Kinases & phosphatases cascade, G-protein signal cascade, Protein Kinase A (cAMP-dependent protein kinase), Structure of G-proteins, Small GTP-binding proteins, GAPs & GEFs,and Phosphatidylinositol signal cascades (Mirza, Plafker, Aston, & Plafker, 2010, p. 2430). Signal protein complexes in the mechanisms may be applicable in testing for the effect of AKT activation on the pathway. It may also incorporate testing if the results and effects are similar before and after the pathway activation. Otherwise, an experimental investigation on the effects of AKT in a person who is not infected by cancer can be conducted. These methods used to test the activation PI3K signaling inclusive of the representative western blot, densitometric analysis, Areg-dependent activation, and luciferase assays (Mirza, Plafker, Aston, & Plafker, 2010). The proven methods incorporate the G Protein Signal Cascade and Phosphatidylinositol signal cascade. Finally, the activation level of the pathway can be varied to determine whether the effect on the target proteins has a proportional relationship with the discussed level of activation.
References
Hennessy, B. T., Smith, D. L., Ram, P. T., Lu, Y., & Mills, G. B. (2005). Exploiting the PI3K/AKT pathway for cancer drug discovery. Nature reviews Drug discovery, 4(12), 988-1004.
Mirza, S., Plafker, K. S., Aston, C., &Plafker, S. M. (2010). Expression and distribution of the class III ubiquitin-conjugating enzymes in the retina.Molecular Vision, 16, 2425–2437.
Nagata, Y., Lan, K. H., Zhou, X., Tan, M., Esteva, F. J., Sahin, A. A., &Hortobagyi, G. N. (2004). PTEN activation contributes to tumor inhibition by trastuzumab, and loss of PTEN predicts trastuzumab resistance in patients.Cancer cell, 6(2), 117-127.
Toker, A., &Marmiroli, S. (2014). Signaling specificity in the Akt pathway in biology and disease. Advances in biological regulation, 55, 28-38.
