Both the sequence and length of the C terminus of PEN-2 are critical for intermolecular interactions and function of presenilin complexes
JOURNAL OF BIOLOGICAL CHEMISTRY
Authors: Hasegawa, H; Sanjo, N; Chen, FS; Gu, YJ; Shier, C; Petit, A; Kawarai, T; Katayama, T; Schmidt, SD; Mathews, PM; Schmitt-Ulms, G; Fraser, PE; St George-Hyslop, P
Abstract
Presenilin 1 or presenilin 2, nicastrin, APH-1, and PEN-2 form high molecular weight complexes that play a pivotal role in the cleavage of various Type I transmembrane proteins, including the beta-amyloid precursor protein. The specific function of PEN-2 is unclear. To explore its function and intermolecular interactions, we conducted deletion and mutagenesis studies on a series of conserved residues at the C terminus of PEN-2. These studies suggest that: 1) both the presence and amino acid sequence of the conserved DYLSF domain at the C terminus of PEN-2 (residues 90-94) is critical for binding PEN-2 to other components in the presenilin complex and 2) the overall length of the exposed C terminus is critical for functional gamma-secretase activity.
Temporal assessment of traumatic axonal injury in the rat corpus callosum and optic chiasm
BRAIN RESEARCH
Authors: Zakaria, Nisrine; Kallakuri, Srinivasu; Bandaru, Sharath; Cavanaugh, John M.
Abstract
Impaired axoplasmic transport (IAT) and neurofilament compaction (NFC), two common axonal pathology processes involved in traumatic axonal injury (TAI), have been well characterized. TAI is found clinically and in animal models in brainstem white matter (WM) tracts and in the corpus callosum (CC), optic chiasm (Och), and internal capsule. Previous published quantitative studies of the time course of TAI expression induced by the Marmarou impact acceleration model have been limited to the brainstem. Accordingly, this study assessed the extent of IAT and NFC in the CC and Och at 8 h, 28 h, 3 days and 7 days after traumatic brain injury (TB!) induction by the Marmarou impact acceleration model. IAT peak density was observed at 8 h in the CC and 28 h in the Och post-TBI. NFC peak density was observed at 28 h in both structures. The density of IAT and NFC decreased with increasing survival time in both structures. The NFC density time profile followed a similar trend in both the Och and CC, whereas the IAT density time profile was variable between the Och and CC. Furthermore, a strong linear relationship was observed between IAT and NFC in the CC but not in the Och. These findings highlight the heterogeneity of TAI as evidenced by variable IAT and NFC injury time profiles in each anatomical structure. This variability indicates the requirement of multiple markers for a comprehensive TAI evaluation and multiple targeted treatments for TAI polypathology within its therapeutic window time frame. (c) 2012 Elsevier B.V. All rights reserved.