Ca2+ functions as a second messenger in all eukaryotes. Such Ca2+ signaling is used to coordinate plant responses to numerous stimuli, both developmental and environmental. Ca2+ signals are often transduced via the action of the ubiquitous Ca2+ sensor calmodulin (CaM). CaM-dependent protein phosphorylation forms an important component of such signal transduction pathways, including that regulating the initiation and development of symbiotic rhizobial nodules in legumes such as soybean (Glycine max). To further understand the role of Ca2+/CaM during nodule organogenesis, a nodule cDNA expression library was screened using radiolabeled CaM as a probe to identify novel CaM-binding proteins (CaMBPs). This screen resulted in the identification of a previously uncharacterized receptor-like kinase, termed GmCaMK1. The CaM-binding domain (CaMBD) of GmCaMK1 is located in a 24 residue region of GmCaMK1, which overlaps with the subdomain XI of a conserved Ser/Thr kinase domain. This CaMBD bound CaM in a Ca2+-dependent manner, and with high affinity (Kd = 1.4 nM). Furthermore, two hydrophobic residues (V372 and L375) were identified as critical for GmCaMK1-CaM interaction. Recombinant GmCaMK1 exhibited protein kinase activity in vitro, with autophosphorylation activity unaffected by the presence or absence of Ca2+/CaM. GmCaMK1 expression is enriched in developing nodules and main roots, and highest expression level was observed in lateral roots. While the function of CaM-binding to GmCaMK1 remains unclear, the affinity and Ca2+-dependence of the GmCaMK1-CaM interaction strongly suggests that GmCaMK1 is a physiologically relevant CaM target. The Arabidopsis ortholog of GmCaMK1, AtCaMK1 also bound CaM when expressed as a recombinant protein. GmCaMK1 is part of a multi-member family in soybean, as are putative homologs across taxa, suggesting that this is a novel, conserved family of CaMBPs. / Thesis (Master, Biology) -- Queen's University, 2010-01-28 16:00:48.69

Diss. (sammanfattning) Stockholm : Karolinska institutet, 2007. / Härtill 4 uppsatser.

Diss. (sammanfattning) Uppsala : Uppsala universitet, 2008. / Härtill 4 uppsatser.

Thesis (Ph. D.)--University of Washington, 2004. / Vita. Includes bibliographical references (leaves 113-124).

Thesis (Ph. D.)--University of Virginia, 1999. / Includes bibliographical references (p. 237-268). Also available online through Digital Dissertations.

Im Rahmen der vorliegenden Arbeit wurde eine mögliche Beteiligung der Protein-Translokase des Endoplasmatischen Retikulums aus Canis familiaris an der Vermittlung eines passiven Calcium-Ausstromes aus dem ER-Lumen untersucht. Der Sec61-Komplex konstituiert eine ionenpermeable Pore im Translokon des Endoplasmatischen Retikulums. Der Kanal zeigt eine hohe Dynamik im Schaltverhalten mit einer Vielzahl von Unterleitwerten, deren Mittelwerte gut mit publizierten Daten übereinstimmen. Zudem besitzt die Pore eine geringe Anionenselektivität in Experimenten mit KCl-Lösungen. Unter Verwendung von CaCl2- und MgCl2-Elektrolyten steigt diese deutlich an, was in vivo den Sec61-vermittelten, passiven Calcium-Ausstrom aus dem ER limitieren kann. Calmodulin (CaM) konnte im Rahmen der vorliegenden Arbeit als potenter Effektor des Sec61-Kanales identifiziert werden. Das Protein vermittelt ein Calcium-abhängiges, nahezu vollständiges Schließen des Kanals, während Calcium-freies ApoCalmodulin keinen Effekt auf den Offenzustand hat. Mittels Fluoreszenz-Korrelations-Spektroskopie konnte gezeigt werden, dass ein IQ-Motiv als putative Calmodulin-Bindestelle im cytosolischen N-Terminus der Sec61alpha-Untereinheit Ca2 -CaM mit nanomolarer Affinität bindet, eine Interaktion mit ApoCaM hingegen erst bei wesentlich höheren Konzentrationen stattfindet. Die CaM-vermittelte, negative Feedback-Regulation des Sec61-Komplexes durch Calcium legt einen CDI- (calcium-dependent inactivation) Mechanismus nahe, der die Membranbarriere des Endoplasmatischen Retikulums auch in Anwesenheit des weiten Translokonkanals aufrecht erhält.Vergleichende Experimente haben zudem ergeben, dass der Sec61-Kanal aus Saccharomyces cerevisiae im Hinblick auf die grundsätzlichen elektrophysiologischen Eigenschaften übereinstimmende Charakteristika mit dem Komplex aus Canis familiaris zeigt.

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In traditional Pavlovian fear conditioning paradigms, animals associate a neutral sensory cue, such as a sound or light, with an aversive stimulus like a mild electric shock. Over time, they develop a conditioned fear response to the cue alone. However, in the real world, cues that predict danger usually lack temporal predictability. Environmental unpredictability is known to enhance aversive memory. The basolateral amygdala (BLA) plays a critical role in forming aversive memories, mediating the convergence of multimodal sensory information. Previous research on the BLA has shown that different neuronal populations within this area encode valence-associative memories during fear conditioning. Our study aims to explore neuronal network activity within the BLA between predictable versus unpredictable fear conditioning. We employed time-lapse microendoscopic recording techniques to observe BLA neurons' somal calcium activity during fear conditioning and an auditory fear recall test (Chapter 3). We identified neurons with different patterns during these paradigms. 'Memory Winners' showed successful convergence of sensory information consistent with retention of the fear memory, while 'Memory Losers' failed to display conditioned stimulus (CS)-evoked calcium responses during fear recall, indicating a loss of fear memory. A further group, the 'Fear Expression' neurons lacked learning-related plasticity for the tone and shock but showed early CS-evoked activity during fear recall. When we introduced unpredictability during fear conditioning, we observed that the distinct functional classes of neurons remained consistent across paradigms. However, the tone and footshock evoked activity did differ within these neuronal classifications. 'Memory Winners' showed early tone- and shock-evoked increased responsivity, while 'Memory Losers' displayed varying shock responsivity depending on whether the conditioning was predictable or unpredictable. Additionally, we identified an extinction-related functional sub-classification of neurons within the BLA. These included neurons that became less responsive during late extinction trials ('extinction-sensitive'), neurons that showed increased CS-evoked activity during late extinction ('extinction learning'), and neurons that maintained consistent activity levels during fear recall and late extinction trials ('fear sustained'). In a departure from most studies that focus on unexpected stimuli or outcomes, we also investigated whether attention signals, defined by transient changes in BLA neuronal calcium activity, are generated when expected stimuli are omitted (Chapter 4). Using neuronal calcium imaging in the BLA, we found that many amygdala neurons displayed attention signals in a stochastic manner during omitted punishment. These neurons showed enhanced sensory processing and plasticity compared to neurons without error signals. Finally, in Chapter 5, we found that unpredictable fear conditioning affected fear-related freezing behaviors and increased the cFos expression in both the BLA and the lateral septum (LS). This supports the notion that the amygdala is strategically positioned to perceive unpredictable aversive cues during conditioning. Collectively, our findings suggest that unpredictability of aversive cues results in specific alterations in the BLA and other brain areas. / 2025-01-24T00:00:00Z

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No description available.