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Effective cellular function requires both compartmentalization of tasks in space and time, and coordination of those efforts. The endoplasmic reticulum's (ER) expansive and ramifying structure makes it ideally suited to serve as a regulatory platform for organelle-organelle communication through membrane contacts. These contact sites consist of two membranes juxtaposed at a distance less than 30 nm that mediate the exchange of lipids and ions without the need for membrane fission or fusion, a process distinct from classical vesicular transport. Membrane contact sites are positioned by organelle-specific membrane-membrane tethering proteins and contain a growing number of additional proteins that organize information transfer to shape membrane identity. Here we briefly review the role of ER-containing membrane junctions in two important cellular functions: calcium signalling and phosphoinositide processing.

Endoplasmic reticulum-plasma membrane (ER-PM) contact sites play an integral role in cellular processes such as excitation-contraction coupling and store-operated calcium entry (SOCE). Another ER-PM assembly is one tethered by the extended synaptotagmins (E-Syt). We have discovered that at steady state, E-Syt2 positions the ER and Sac1, an integral ER membrane lipid phosphatase, in discrete ER-PM junctions. Here, Sac1 participates in phosphoinositide homeostasis by limiting PM phosphatidylinositol 4-phosphate (PI(4)P), the precursor of PI(4,5)P2 Activation of G protein-coupled receptors that deplete PM PI(4,5)P2disrupts E-Syt2-mediated ER-PM junctions, reducing Sac1's access to the PM and permitting PM PI(4)P and PI(4,5)P2to recover. Conversely, depletion of ER luminal calcium and subsequent activation of SOCE increases the amount of Sac1 in contact with the PM, depleting PM PI(4)P. Thus, the dynamic presence of Sac1 at ER-PM contact sites allows it to act as a cellular sensor and controller of PM phosphoinositides, thereby influencing many PM processes.

Plasma membrane (PM) phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] regulates the activity of many ion channels and other membrane-associated proteins. To determine precursor sources of the PM PI(4,5)P2 pool in tsA-201 cells, we monitored KCNQ2/3 channel currents and translocation of PHPLCδ1 domains as real-time indicators of PM PI(4,5)P2, and translocation of PHOSH2×2, and PHOSH1 domains as indicators of PM and Golgi phosphatidylinositol 4-phosphate [PI(4)P], respectively. We selectively depleted PI(4)P pools at the PM, Golgi, or both using the rapamycin-recruitable lipid 4-phosphatases. Depleting PI(4)P at the PM with a recruitable 4-phosphatase (Sac1) results in a decrease of PI(4,5)P2 measured by electrical or optical indicators. Depleting PI(4)P at the Golgi with the 4-phosphatase or disrupting membrane-transporting motors induces a decline in PM PI(4,5)P2. Depleting PI(4)P simultaneously at both the Golgi and the PM induces a larger decrease of PI(4,5)P2. The decline of PI(4,5)P2 following 4-phosphatase recruitment takes 1-2 min. Recruiting the endoplasmic reticulum (ER) toward the Golgi membranes mimics the effects of depleting PI(4)P at the Golgi, apparently due to the trans actions of endogenous ER Sac1. Thus, maintenance of the PM pool of PI(4,5)P2 appears to depend on precursor pools of PI(4)P both in the PM and in the Golgi. The decrease in PM PI(4,5)P2 when Sac1 is recruited to the Golgi suggests that the Golgi contribution is ongoing and that PI(4,5)P2 production may be coupled to important cell biological processes such as membrane trafficking or lipid transfer activity.

The author's first reaction to learning that the new science standards adopted in Minnesota included engineering was fear and apprehension. She couldn't picture what an engineering project would look like at the elementary level. As a K-5 elementary science specialist, it was now her job to figure out how to incorporate engineering in their curriculum. High-quality professional development, conversations with colleagues, and web research have helped her create a vision and plan for how engineering with elementary students might look. Her role as science specialist is to extend and enhance the learning done in classrooms. In this particular example, students came to her having already completed a unit on balance and motion. Students could describe a variety of types of motion and how different forces act on objects, as well as a basic understanding of gravity. Building on their knowledge, she created a way for students to apply these concepts in a different situation. This unit took a total of five, 50-minute class periods. To help with supplies, a letter was sent home to parents asking for materials such as toilet paper tubes, bottle caps, and soft cardboard packages (i.e., cereal boxes) or egg cartons. In this unit, students explore engineering with model cars and ramps. Students have found success with this project as they see, firsthand, how the properties of supplies affect their design. In addition, this practice with the engineering design process has provided an opportunity for students to see that they can be successful engineers and that engineering is an important part of their daily lives. (Contains 1 figure and 4 online resources.)

Elementary students make great scientists. They are natural questioners and observers. Capitalizing on this natural curiosity and wonderment, the authors have developed a method of doing inquiry investigations with students that many teachers have found practical and user friendly. Their belief is that full inquiry lessons serve as a vital method for students to grasp science content in a meaningful way, establish confidence that they are scientists, and help address national standards. In this article, the authors provide five guidelines for designing inquiry lessons within any grade level. (Contains 6 figures.)

The signaling phosphoinositide phosphatidylinositol 4,5-bisphosphate ([PIP.sub.2]) is synthesized in two steps from phosphatidylinositol by lipid kinases. It then interacts with KCNQ channels and with pleckstrin homology (PH) domains among many other physiological protein targets. We measured and developed a quantitative description of these metabolic and protein interaction steps by perturbing the [PIP.sub.2] pool with a voltage-sensitive phosphatase (VSP). VSP can remove the 5-phosphate of [PIP.sub.2] with a time constant of [tau] doi/ 10.1085/jgp.200910345

G protein--coupled receptors (GPCRs) mediate responses to external stimuli in various cell types. Early events, such as the binding of ligand and G proteins to the receptor, nucleotide exchange (NX), and GTPase activity at the G[alpha] subunit, are common for many different GPCRs. For [G.sub.q]-coupled [M.sub.1] muscarinic (acetylcholine) receptors ([M.sub.1]Rs), we recently measured time courses of intermediate steps in the signaling cascade using Forster resonance energy transfer (FRET). The expression of FRET probes changes the density of signaling molecules. To provide a full quantitative description of [M.sub.1]R signaling that includes a simulation of kinetics in native (tsA201) cells, we now determine the density of FRET probes and construct a kinetic model of [M.sub.1]R signaling through [G.sub.q] to activation of phospholipase C (PLC). Downstream effects on the trace membrane lipid phosphatidylinositol 4,5-bisphosphate ([PIP.sub.2]) and [PIP.sub.2]-dependent KCNQ2/3 current are considered in our companion paper in this issue (Falkenburger et al. 2010. J. Gen. Physiol. doi: 10.1085/jgp.200910345). By calibrating their fluorescence intensity, we found that we selected transfected cells for our experiments with ~3,000 fluorescently labeled receptors, G proteins, or PLC molecules per [[micro]m.sup.2] of plasma membrane. Endogenous levels are much lower, 1-40 per [[micro]m.sup.2]. Our kinetic model reproduces the time courses and concentration--response relationships measured by FRET and explains observed delays. It predicts affinities and rate constants that align well with literature values. In native tsA201 cells, much of the delay between ligand binding and PLC activation reflects slow binding of G proteins to receptors. With [M.sub.1]R and G[beta] FRET probes overexpressed, 10% of receptors have G proteins bound at rest, rising to 73% in the presence of agonist. In agreement with previous work, the model suggests that binding of PLC to G[[alpha].sub.q] greatly speeds up NX and GTPase activity, and that PLC is maintained in the active state by cycles of rapid GTP hydrolysis and NX on G[[alpha].sub.q] subunits hound to PLC. doi/ 10.1085/jgp.200910344

G protein--coupled receptors initiate signaling cascades. [M.sub.1] muscarinic receptor ([M.sub.1]R) activation couples through G[[alpha].sub.q] to stimulate phospholipase C (PLC), which cleaves phosphatidylinositol 4,5-bisphosphate ([PIP.sub.2]). Depletion of [PIP.sub.2] closes [PIP.sub.2]-requiring Kv7.2/7.3 potassium channels (M current), thereby increasing neuronal excitability. This modulation of M current is relatively slow (6.4 s to reach within 1/e of the steady-state value). To identify the rate-limiting steps, we investigated the kinetics of each step using pairwise optical interactions likely to represent fluorescence resonance energy transfer for [M.sub.1]R activation, [M.sub.1]R/G[beta] interaction, G[[alpha].sub.q]/G[beta] separation, G[[alpha].sub.q]/PLC interaction, and [PIP.sub.2] hydrolysis. Electrophysiology was used to monitor channel closure. Time constants for [M.sub.1]R activation (

Keywords: right to the city; urban appropriation; capitalism; identity; class struggle EN right to the city urban appropriation capitalism identity class struggle 697 702 6 04/12/22 20220501 NES 220501 Kohn, Margaret (2016). As a serious critique from the Left, rights within the liberal state are contradictory in that they seem to give to the people but reinforce a state's mechanism of domination. Kohn provides an excellent summary for this essay on struggle and appropriation in light its evaluation of "the public", of democracy and deliberation, and the strengths but also the shortcoming of rights' claims. "Lefebvre argued that the power to make urban spaces, which he viewed as the control points of modern capitalism", writes Herod, "must be wrested from capital and the state and located instead in the hands of the working-class people" (Herod, p. 197). [Extracted from the article]

Phosphatidylinositol(4,5)-bisphosphate (PtdInsP2) is an important modulator of many cellular processes, and its abundance in the plasma membrane is closely regulated. We examined the hypothesis that members of the Dishevelled scaffolding protein family can bind the lipid kinases phosphatidylinositol 4-kinase (PI4K) and phosphatidylinositol 4-phosphate 5-kinase (PIP5K), facilitating synthesis of PtdInsP2 directly from phosphatidylinositol. We used several assays for PtdInsP2 to examine the cooperative function of phosphoinositide kinases and the Dishevelled protein Dvl3 in the context of two receptor signaling cascades. Simultaneous overexpression of PI4KIIIα (also known as PI4KA) and PIP5KIγ (also known as PIP5K1C) had a synergistic effect on PtdInsP2 synthesis that was recapitulated by overexpression of Dvl3. Increasing the activity of Dvl3 by overexpression increased resting plasma membrane PtdInsP2. Knockdown of Dvl3 reduced resting plasma membrane PtdInsP2 and slowed PtdInsP2 resynthesis following receptor activation. We confirm that Dvl3 promotes coupling of PI4KIIIα and PIP5KIγ and show that this interaction is essential for efficient resynthesis of PtdInsP2 following receptor activation. [ABSTRACT FROM AUTHOR]