Exchange proteins activated by cAMP (cyclic AMP) 2 (Epac2) is a guanine nucleotide exchange factor for Rap1, a small G protein involved in many cellular functions, including cell adhesion, differentiation, and exocytosis. Epac2 interacts with Ras-GTP via a Ras association (RA) domain. Previous studies have suggested that the RA domain was dispensable for Epac2 function. Here we show for the first time that Ras and cAMP regulate Epac2 function in a parallel fashion and the Ras-Epac2 interaction is required for the cAMPdependent activation of endogenous Rap1 by Epac2. The mechanism for this requirement is not allosteric activation of Epac2 by Ras but the compartmentalization of Epac2 on the Ras-containing membranes. A computational modeling is consistent with this compartmentalization being a function of both the level of Ras activation and the affinity between Ras and Epac2. In PC12 cells, a well-established model for sympathetic neurons, the Epac2 signaling is coupled to activation of mitogen-activated protein kinases and contributes to neurite outgrowth. Taken together, the evidence shows that Epac2 is not only a cAMP sensor but also a bona fide Ras effector. Coincident detection of both cAMP and Ras signals is essential for Epac2 to activate Rap1 in a temporally and spatially controlled manner.Rap1 is a small GTPase involved in the regulation of multiple cellular functions such as adhesion, differentiation, and exocytosis. Like all small G proteins, Rap1 cycles between a GTP-loaded active state and a GDP-loaded inactive state, which is mediated via the opposing actions of G protein activation proteins that promote hydrolysis of bound GTP to GDP and guanine nucleotide exchange factors (GEFs) that catalyze the exchange of bound GDP for GTP.Exchange proteins activated by cAMP (Epac1 and Epac2) are unique Rap1 GEFs that link cAMP elevation to Rap1 activation (5). This is achieved via the direct binding of cAMP to the Epac protein itself, thereby defining a novel cAMP signaling pathway that is independent of protein kinase A (PKA). Both Epac1 and Epac2 contain a catalytic region and a regulatory region. The catalytic region consists of a CDC25 homology domain that catalyzes Rap1 activation, a REM domain, and a Ras association (RA) domain that lies in between. The regulatory region consists of one or two cAMP binding domains (cNBDs) and a DEP (disheveled, Egl-10, and pleckstrin homology) domain. Under resting conditions, Epac proteins are inactive due to the inhibitory interaction between the regulatory and catalytic regions. The binding of cAMP to the cNBD relieves the intramolecular inhibition by exposing the catalytic site to . Previous studies have been largely focused on the mechanism of cAMP regulation of Epacs. Whether other molecular interactions play a role in Epac regulation is unknown.A number of features of Epac2 distinguish it from Epac1, which suggests distinctive regulatory mechanisms for Epac2. While Epac1 is expressed ubiquitously, Epac2 is highly enriched in neuronal tissues (22). Moreover, Epac1 i...

This paper describes an empirical study of student designers' sketching activities in new product design teams. A comprehensive list of metrics associated with sketches is identified and their relative level of importance at different stages in the design process is evaluated. Correlations between sketching activities, variety of the concept sketches, and design outcomes are presented. Results show the volume of total sketches and the number of 3-dimensional sketches has an increasingly positive effect on the design outcome as the design proceeds from preliminary investigation, through conceptual design, to detailed development and testing. Results also show that there is a statistically significant correlation between the total number of individual journal sketches created during the design process and an individual student's class grade.

Design as a social activity characterized by information exchange, compromise and negotiation frames much of out understanding of the design process. At the heart of this social activity is the development of a shared understanding of the design problem. The design stakeholders jointly form a shared understanding through a process of defining the problem, exploring the space of solutions and searching for information. A shared understanding is a critical element in successful, collaborative design. This paper describes a formal approach for identifying shared understanding in design by analyzing the documentation. By mining the documentation for signatures of a shared understanding, specifically a common frame of reference and a similar voice, a shared language and vocabulary of the design could emerge. Information management tools built around the shared understanding would be more effective in directing and alerting the design team of relevant information.

The NAC family of transcription factors is involved in plant development and various biotic and abiotic stresses. The Arabidopsis thaliana ANAC proteins ANAC060, ANAC040 and ANAC089 are highly homologous based on protein and nucleotide sequence similarity. These three genes are predicted to be membrane bound transcription factors (MTFs) containing a conserved NAC domain but divergent C-terminal regions. The anac060 mutant shows increased dormancy levels when compared to wild type. Mutations in ANAC040 lead to higher seed germination under salt stress and a premature stop codon in ANAC089 Cvi allele results in seeds exhibiting insensitivity to high concentrations of fructose. Thus, these three homologous MTFs confer distinct functions, although all related to germination. To investigate whether the differences in function are caused by a differential spatial or temporal regulation or are the results of differences in the coding sequence (CDS), swapping experiments have been performed in which the promoter and CDS of the three MTFs have been exchanged. Seed dormancy and salt and fructose sensitivity analyses of transgenic swapping lines in mutant backgrounds show that there is functional redundancy between ANAC060 and ANAC040, but not between ANAC060 and ANAC089.

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