Energetic neutral atom response to solar wind dynamic pressure enhancements
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
Authors: Lee, D.-Y.; Ohtani, S.; Brandt, P. C.; Lyons, L. R.
Abstract
We have investigated the response of the ring current to solar wind dynamic pressure (P-dyn) enhancement impacts on the magnetosphere by using energetic neutral atom (ENA) images obtained by the High-Energy Neutral Atom (HENA) imager on board the IMAGE spacecraft. In this work we present several events by distinguishing between pressure events where only the pure compression effects exist (without substorm effects) and those where the substorm is triggered by the Pdyn enhancement, and we find notable differences between these two types of events. First, for the pure compression events, we present four events where the Pdyn increases by similar to 100% to similar to 450% under northward interplanetary magnetic field (IMF) conditions. The Pdyn enhancement results in weak-to-modest ENA emission increases in both the hydrogen and oxygen channels: The total ENA emission rate increases by similar to 25% to similar to 40% relative to averages over the 1-hour period prior to the Pdyn enhancement impact. This ENA enhancement is due to ions adiabatically energized by the compression. The increased ENA emission rate drops as Pdyn decreases, implying that the ENA responses are directly caused by the adiabatic compression and decompression process. Also, the pure compression events lead to overall global, quasi-simultaneous increases of ENA in contrast to pure substorm-induced ENA enhancements that are initially localized in the nightside region followed by the drift effect. Next we present two events where the Pdyn enhancement was similar to 100% and >300%, respectively, under strongly southward IMF conditions, IMF B-z <= -10 nT, and a substorm was triggered. For both events the hydrogen and oxygen ENA emission increase is far more significant than that for the pure compression events, more than 100% even when the low-altitude contribution was excluded. This is primarily owing to energetic ions generated by the triggered substorm, although the compression effect itself occurs as well. Also, the ENA enhancement appears to be not as global in magnetic local time (MLT) as for the pure compression events, because of the predominant substorm effect that starts near midnight and spreads in MLT.
A direct interaction between the large GTPase dynamin-2 and FAK regulates focal adhesion dynamics in response to active Src
MOLECULAR BIOLOGY OF THE CELL
Authors: Wang, Yu; Cao, Hong; Chen, Jing; McNiven, Mark A.
Abstract
Tumor cell migration is supported in part by the cyclic formation and disassembly of focal adhesions (FAs); however, the mechanisms that regulate this process are not fully defined. The large guanosine 5'-triphosphatase dynamin (Dyn) plays an important role in FA dynamics and is activated by tyrosine phosphorylation. Using a novel antibody specific to phospho-dynamin (pDyn-Tyr-231), we found that Dyn2 is phosphorylated at FAs by Src kinase and is recruited to FAs by a direct interaction with the 4.1/ezrin/radizin/moesin domain of focal adhesion kinase (FAK), which functions as an adaptor between Src and Dyn2 to facilitate Dyn2 phosphorylation. This Src-FAK-Dyn2 trimeric complex is essential for FA turnover, as mutants disrupting the formation of this complex inhibit FA disassembly. Importantly, phosphoactivated Dyn2 promotes FA turnover by mediating the endocytosis of integrins in a clathrin-dependent manner. This study defines a novel mechanism of how Dyn2 functions as a downstream effector of FAK-Src signaling in turning over FAs.