While recent studies have generated definitive evidence that high levels of dihydrotestosterone (DHT) is a critical factor that leads to the onset of prostate cancer, we have uncovered the fact that phosphorylation of 95- % identical prostate luminal cell-distributed UGT-2B15 and basal cell-distributed 2B17 are both capable of removing DHT. Moreover, the UGTs are the only known enzymes that remove the DHT related hormones from the prostate. Because DHT-occupied androgen receptors in luminal cells drive the synthesis of >than 200 secretory proteins daily, the over-worked cell becomes compromised and undergoes apoptosis, on average, after 55 days with its cellular replacement derived from basal cell-derived stem cells. Whether this is a genuine basal cell with or without 2B17 on board as the literature indicates basal cell (which is typically the location of 2B17) replaces the departed luminal cells. Whereas we accidentally uncovered the fact that 2B15 activates the endogenous polyubiquitination system in the absence of the Src-kinase enzyme, 2B17, to the contrary, 2B17 cannot carry out this function. Moreover, n Src-free cells 2B15 action completes the polyubiquitination/apoptosis/caspase 8/3 activation as evidence that apoptosis has occurred. In addition, we discovered that 2B15-transfected COS-1 cells treated with Src-inhibitors and/or transfected with one of each of 6 recently identified anti-UGT-detected E3-ligases also undergoes more robust polyubiquitination/caspase activation. Moreover, human RWPE-1 prostate cells that have a low level of 2B15 also under goes apoptosis when treated with a Src inhibitor. (Background information indicates Kock out mice lacking the stratifying-P63 gene fail to form prostate luminal cells.) Our mutagenesis data indicate very few changes have led to the important differences between the two proteins, which were established by mass spectrometric analysis enabling us to make comparisons between 2B15 and 2B17. A proteomic search of E3 ligases with highly specific anti-UGT detected affinity purified UGT in contact with differential affinities toward various E3 ligases. This study already has implications about the use of Src inhibitors for prostate cancer treatment. Whereas evaluations of our studies that characterized 2B17 with respect to its required regulated phosphorylation, we accumulated mass spectrometric analysis data that revealed a unique triad phosphorylated site the isozyme. Its expression in Src- containing and Src-free cells demonstrated it is typically down-regulated in Src-containing cells, but are 2-fold more active in Src-free cells, which indicates it responds oppositely to 2B15. Hence, we have completed two different studies that show 2B17 receives positive support from PKCalpha and negative support from the combination of PKCepsilon and Src. In general, regulated phosphorylation of human DHT-metabolizing UGT-2B17 depresses its constitutive activity. Thirdly, we have 2 mouse UGTs that convert endogenous and exogenous agents that the single human UGT2B7 is capable of handling. Moreover, these mouse Ugts that metabolize estrogen derivatives are primarily distributed in prostate tissues. The implication of these observations warrant further investigations to determine if the estrogen-alpha and estrogen-beta receptors recently carried out in our laboratory in mouse prostate control pro- and/or anti- apoptotic effects, which we are analyzing for in the ubiquitination studies described above for 2B15.
|Mitra, Partha S; Basu, Nikhil K; Owens, Ida S (2009) Src supports UDP-glucuronosyltransferase-2B7 detoxification of catechol estrogens associated with breast cancer. Biochem Biophys Res Commun 382:651-6|
|Banerjee, Rajat; Pennington, Matthew W; Garza, Amanda et al. (2008) Mapping the UDP-glucuronic acid binding site in UDP-glucuronosyltransferase-1A10 by homology-based modeling: confirmation with biochemical evidence. Biochemistry 47:7385-92|
|Basu, Nikhil K; Kole, Labanyamoy; Basu, Mousumi et al. (2008) The major chemical-detoxifying system of UDP-glucuronosyltransferases requires regulated phosphorylation supported by protein kinase C. J Biol Chem 283:23048-61|