ABSTRACT
Prostate cancer (PCa) is one of the most prevalent types of cancer in men worldwide; however, the main diagnostic tests available for PCa have limitations and a biopsy is required for histopathological confirmation of the disease. Prostate-specific antigen (PSA) is the main biomarker used for the early detection of PCa, but an elevated serum concentration is not cancer-specific. Therefore, there is a need for the discovery of new non-invasive biomarkers that can accurately diagnose PCa. The present study used trichloroacetic acid-induced protein precipitation and liquid chromatography-mass spectrometry to profile endogenous peptides in urine samples from patients with PCa (n=33), benign prostatic hyperplasia (n=25) and healthy individuals (n=28). Receiver operating characteristic curve analysis was performed to evaluate the diagnostic performance of urinary peptides. In addition, Proteasix tool was used for in silico prediction of protease cleavage sites. Five urinary peptides derived from uromodulin were revealed to be significantly altered between the study groups, all of which were less abundant in the PCa group. This peptide panel showed a high potential to discriminate between the study groups, resulting in area under the curve (AUC) values between 0.788 and 0.951. In addition, urinary peptides outperformed PSA in discriminating between malignant and benign prostate conditions (AUC=0.847), showing high sensitivity (81.82%) and specificity (88%). From in silico analyses, the proteases HTRA2, KLK3, KLK4, KLK14 and MMP25 were identified as potentially involved in the degradation of uromodulin peptides in the urine of patients with PCa. In conclusion, the present study allowed the identification of urinary peptides with potential for use as non-invasive biomarkers in PCa diagnosis.
ABSTRACT
The Arabidopsis thaliana endogenous elicitor peptides (AtPeps) are released into the apoplast after cellular damage caused by pathogens or wounding to induce innate immunity by direct binding to the membrane-localized leucine-rich repeat receptor kinases, PEP RECEPTOR1 (PEPR1) and PEPR2. Although the PEPR-mediated signaling components and responses have been studied extensively, the contributions of the subcellular localization and dynamics of the active PEPRs remain largely unknown. We used live-cell imaging of the fluorescently labeled and bioactive pep1 to visualize the intracellular behavior of the PEPRs in the Arabidopsis root meristem. We found that AtPep1 decorated the plasma membrane (PM) in a receptor-dependent manner and cointernalized with PEPRs. Trafficking of the AtPep1-PEPR1 complexes to the vacuole required neither the trans-Golgi network/early endosome (TGN/EE)-localized vacuolar H(+)-ATPase activity nor the function of the brefeldin A-sensitive ADP-ribosylation factor-guanine exchange factors (ARF-GEFs). In addition, AtPep1 and different TGN/EE markers colocalized only rarely, implying that the intracellular route of this receptor-ligand pair is largely independent of the TGN/EE. Inducible overexpression of the Arabidopsis clathrin coat disassembly factor, Auxilin2, which inhibits clathrin-mediated endocytosis (CME), impaired the AtPep1-PEPR1 internalization and compromised AtPep1-mediated responses. Our results show that clathrin function at the PM is required to induce plant defense responses, likely through CME of cell surface-located signaling components.