Diacylglycerol Kinase δ Suppresses ER-to-Golgi Traffic via Its SAM and PH Domains

We report here that the anterograde transport from the endoplasmic reticulum (ER) to the Golgi was markedly suppressed by diacylglycerol kinase δ (DGKδ) that uniquely possesses a pleckstrin homology (PH) and a sterile α motif (SAM) domain. A low-level expression of DGKδ in NIH3T3 cells caused redistribution into the ER of the marker proteins of the Golgi membranes and the vesicular-tubular clusters (VTCs). In this case DGKδ delayed the ER-to-Golgi traffic of vesicular stomatitis virus glycoprotein (VSV G) and also the reassembly of the Golgi apparatus after brefeldin A (BFA) treatment and washout. DGKδ was demonstrated to associate with the ER through its C-terminal SAM domain acting as an ER-targeting motif. Both of the SAM domain and the N-terminal PH domain of DGKδ were needed to exert its effects on ER-to-Golgi traffic. Kinase-dead mutants of DGKδ were also effective as the wild-type enzyme, suggesting that the catalytic activity of DGK was not involved in the present observation. Remarkably, the expression of DGKδ abrogated formation of COPII-coated structures labeled with Sec13p without affecting COPI structures. These findings indicate that DGKδ negatively regulates ER-to-Golgi traffic by selectively inhibiting the formation of ER export sites without significantly affecting retrograde transport

Identification of a Novel Light Intermediate Chain (D2LIC) for Mammalian Cytoplasmic Dynein 2

The diversity of dynein's functions in mammalian cells is a manifestation of both the existence of multiple dynein heavy chain isoforms and an extensive set of associated protein subunits. In this study, we have identified and characterized a novel subunit of the mammalian cytoplasmic dynein 2 complex. The sequence similarity between this 33-kDa subunit and the light intermediate chains (LICs) of cytoplasmic dynein 1 suggests that this protein is a dynein 2 LIC (D2LIC). D2LIC contains a P-loop motif near its NH(2) terminus, and it shares a short region of similarity to the yeast GTPases Spg1p and Tem1p. The D2LIC subunit interacts specifically with DHC2 (or cDhc1b) in both reciprocal immunoprecipitations and sedimentation assays. The expression of D2LIC also mirrors that of DHC2 in a variety of tissues. D2LIC colocalizes with DHC2 at the Golgi apparatus throughout the cell cycle. On brefeldin A-induced Golgi fragmentation, a fraction of D2LIC redistributes to the cytoplasm, leaving behind a subset of D2LIC that is localized around the centrosome. Our results suggest that D2LIC is a bona fide subunit of cytoplasmic dynein 2 that may play a role in maintaining Golgi organization by binding cytoplasmic dynein 2 to its Golgi-associated cargo

Selection of the InSight Landing Site

The selection of the Discovery Program InSight landing site took over four years from initial identification of possible areas that met engineering constraints, to downselection via targeted data from orbiters (especially Mars Reconnaissance Orbiter (MRO) Context Camera (CTX) and High-Resolution Imaging Science Experiment (HiRISE) images), to selection and certification via sophisticated entry, descent and landing (EDL) simulations. Constraints on elevation (≤−2.5 km for sufficient atmosphere to slow the lander), latitude (initially 15°S–5°N and later 3°N–5°N for solar power and thermal management of the spacecraft), ellipse size (130 km by 27 km from ballistic entry and descent), and a load bearing surface without thick deposits of dust, severely limited acceptable areas to western Elysium Planitia. Within this area, 16 prospective ellipses were identified, which lie ∼600 km north of the Mars Science Laboratory (MSL) rover. Mapping of terrains in rapidly acquired CTX images identified especially benign smooth terrain and led to the downselection to four northern ellipses. Acquisition of nearly continuous HiRISE, additional Thermal Emission Imaging System (THEMIS), and High Resolution Stereo Camera (HRSC) images, along with radar data confirmed that ellipse E9 met all landing site constraints: with slopes \u3c15° at 84 m and 2 m length scales for radar tracking and touchdown stability, low rock abundance (\u3c10 %) to avoid impact and spacecraft tip over, instrument deployment constraints, which included identical slope and rock abundance constraints, a radar reflective and load bearing surface, and a fragmented regolith ∼5 m thick for full penetration of the heat flow probe. Unlike other Mars landers, science objectives did not directly influence landing site selection