Protein phosphatase 2A (PP2A) is a multifunctional serine/threonine phosphatase that is critical to many cellular processes including development, neuronal signaling, cell cycle regulation, and viral transformation. PP2A has been implicated in Ca 2؉ -dependent signaling pathways, but how PP2A is targeted to these pathways is not understood. We have identified two calmodulin (CaM)-binding proteins that form stable complexes with the PP2A A/C heterodimer and may represent a novel family of PP2A B-type subunits. These two proteins, striatin and S/G 2 nuclear autoantigen (SG2NA), are highly related WD40 repeat proteins of previously unknown function and distinct subcellular localizations. Striatin has been reported to associate with the postsynaptic densities of neurons, whereas SG2NA has been reported to be a nuclear protein expressed primarily during the S and G 2 phases of the cell cycle. We show that SG2NA, like striatin, binds to CaM in a Ca 2؉ -dependent manner. In addition to CaM and PP2A, several unidentified proteins stably associate with the striatin-PP2A and SG2NA-PP2A complexes. Thus, one mechanism of targeting and organizing PP2A with components of Ca 2؉-dependent signaling pathways may be through the molecular scaffolding proteins striatin and SG2NA. PP2A,1 an essential serine/threonine protein phosphatase found in all eukaryotic cells, regulates a wide variety of important cellular events, including DNA replication, transcription, translation, development, neuronal signaling and progression of the cell cycle (for reviews see Refs. 1-3). The PP2A heterotrimer consists of a catalytic (C) subunit, a structural (A) subunit, and a regulatory (B-type) subunit (4). Although relatively few C-and A-type subunits have been identified, multiple B-type subunits exist, including B (or B55), BЈ (or B56), and BЈЈ (or PR72/130) classes (5-9). To enable utilization of this phosphatase for numerous substrates in different pathways, PP2A is regulated at multiple levels, including covalent modifications, interaction with inhibitory proteins and lipids, and association with the various B-type subunits. For example, BЈ subunits were recently shown to target PP2A to the adenomatous polyposis coli tumor suppressor scaffolding protein, physically associating PP2A with specific substrates and thus regulating Wnt-␤-catenin signaling (10).PP2A has also been shown to form complexes with CaM-dependent kinase IV (CaMKIV) (11), suggesting a role for PP2A in Ca 2ϩ -dependent signaling. This possibility is further supported by patch clamp experiments with both neuronal (12) and smooth muscle cells (13) that have used both okadaic acid and recombinant PP2A C subunit to implicate PP2A in the regulation of calcium-activated potassium channels and L-type Ca 2ϩ channels (14).To better understand how PP2A is targeted to various microenvironments and signal transduction pathways within the cell, we have looked for additional PP2A targeting subunits. Here we report the identification of two PP2A-associated proteins that may represent a novel ...

Adoptive transfer of high-affinity chimeric antigen receptor (CAR) T cells targeting hematological cancers has yielded impressive clinical results. However, safety concerns regarding target expression on healthy tissue and poor efficacy have hampered application to solid tumors. Here, a panel of affinity-variant CARs were constructed targeting overexpressed ICAM-1, a broad tumor biomarker, using its physiological ligand, LFA-1. Anti-tumor T cell potency in vitro was directly proportional to CAR affinity and ICAM-1 density. In a solid tumor mouse model allowing simultaneous monitoring of anti-tumor potency and systemic off-tumor toxicity, micromolar affinity CAR T cells demonstrated superior anti-tumor efficacy and safety compared to their nanomolar counterparts. Longitudinal T cell tracking by PET/CT and concurrent cytokine measurement revealed superior expansion and contraction kinetics of micromolar affinity CAR T cells. Therefore, we developed an ICAM-1 specific CAR with broad anti-tumor applicability that utilized a reduced affinity targeting strategy to significantly boost efficacy and safety.

Across all waking hours of 1 d, step counts differ between devices. The SW, regardless of settings, was the most accurate method of counting steps.

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