Identification and Partial Characterization of Two Populations of Prostasomes by a Combination of Dynamic Light Scattering and Proteomic Analysis

Abstract

Prostasomes are vesicles secreted by prostate epithelial cells and are found in abundance in the semen. Here we characterized two different prostasome populations isolated from human seminal fluid. Prostasomes were isolated using differential centrifugation, while dynamic light scattering (DLS) was used to characterize their size and size distribution. Their protein content was analyzed using two-dimensional electrophoresis and mass spectrometry. DLS showed two distinct prostasome subpopulations in centrifuged seminal plasma, with an average hydrodynamic radius of 80 and 300 nm. The larger population was isolated after centrifugation at 20,000 × g (P20), while the smaller one was recovered at 100,000 × g (P100). The two fractions had a similar lipid composition, showing an elevated content of sphingomyelin and cholesterol. The P100 vesicles showed a significant over-expression of proteins involved in the endosomal sorting complexes required for transport (ESCRT) machinery such as Alix, TSG101, and syntenin-1. Some proteins possibly involved in prostate cancer were present only in one specific population (TMPRSS2 in P100 and VCP in P20). The different size and protein profile in the two subpopulations of prostasomes might support differential roles of the semen vesicles toward the target cells, and/or different secretion pathways from the organ of origin.

Clinical Evaluation of Urine Prostatic Exosomal Protein in the Diagnosis of Chronic Prostatitis

“…There appear to be 2 distinct subpopulations of prostasomes, which have a mean diameter of 150 nm and range from 40 to 500 nm under electron microscopy [14]. More recently, 2 distinct prostasome subpopulations in centrifuged seminal plasma were detected with dynamic light scattering, with an average hydrodynamic radius of 80 and 300 nm [15]. Prostasomes comprise a variety of proteins, lipid compounds (the majority of which is sphingomyelin) and nucleic acids (including mRNA, miRNA, and small DNA fragments).…”

Extracellular Vesicles in Prostate Cancer Carcinogenesis, Diagnosis, and Management

“…Of note, one study suggested that production of prostasomes in prostate cancer cells is inversely correlated with the Gleason score ( 83 ). Other studies demonstrated differential expression in prostasomes derived from normal or cancer prostate cells ( 44 – 46 , 49 , 55 ).…”

Bone marrow-derived mesenchymal stromal cell: what next?

“…They present characteristic proteins like the tetraspanin family members (CD63, CD81, and CD9), heat-shock proteins, 31 and endosomes such as Alix and TSG101. 32 Exosomes are released in answer to the microenvironment modifications after primary endosome formation. MVB membrane fuses with the plasmatic membrane, releasing exosomes into the environment where they can be overtaken by other cells in order to mediate a paracrine communication.…”