PP2A-C may be a promising candidate for postmortem interval estimation.

Abstract

Determining the postmortem interval (PMI) is an important task in forensic pathology. However, a reliable means of determining the PMI between 24h and approximately 7days after death has not yet been established. A previous study demonstrated that subunit A of protein phosphatase 2A (PP2A-A) is a promising candidate to estimate the PMI during the first 96h. However, more detailed work is still needed to investigate PP2A's function in PMI estimation. PP2A is a serine/threonine phosphatase consisting of three subunits (PP2A-A, PP2A-B, and PP2A-C), and its activation is reflected by Tyr-307 phosphorylation of the catalytic subunit (P-PP2A-C). In this study, we speculated that the other two subunits of PP2A and the activation of PP2A may play different roles in estimating the PMI. For this purpose, mice were euthanized and stored at different temperatures (4, 15, and 25°C). At each temperature, the musculus vastus lateralis was collected at different time points (0, 24, 48, and 96h) to investigate the degradation of PP2A-B, PP2A-C, and P-PP2A-C (Tyr-307). Homocysteine (Hcy) was used to establish a hyperhomocysteinemia animal model to explore the effects of plasma Hcy on PMI estimation. The data showed not only that PP2A-C was more stable than PP2A-B, but also that it was not affected by homocysteine (Hcy). These characteristics make PP2A-C a promising candidate for short-term (24h to 48h) PMI estimation.