Post-translational modifications such as phosphorylation and palmitoylation play important roles for the function and regulation of receptors coupled to heterotrimeric guanyl nucleotide-binding proteins. Here we demonstrate that the human endothelin receptor A (ET A ) incorporates [ 3 H]palmitate. Mutation of a cluster of five cysteine residues present in the cytoplasmic tail of ET A into serine or alanine residues completely prevented palmitoylation of the receptor. The ligand binding affinity of the non-palmitoylated ET A mutants was essentially unchanged as compared to the palmitoylated wild type ET A suggesting that the replacement of the cysteine residues did not alter the overall structure of the receptor. Furthermore, the ligand-induced stimulation of adenylyl cyclase by the mutant ET A was unaffected by the mutation. In contrast, the mutated nonpalmitoylated receptors but not the wild type receptor failed to stimulate phosphatidylinositol hydrolysis by phospholipase C activation upon challenge by endothelin-1. Furthermore, the mutant receptors failed to stimulate the ligand-induced transient increase in the cytoplasmic calcium seen with the wild type ET A . Endothelin-1 induced mitogenic stimuli via the wild type receptors but not through the mutated receptors suggesting an important role for phospholipase C in this signal transduction pathway. The differential regulation of distinct signal transduction pathways by posttranslational modification suggests that palmitoylation of the ET A provides a novel mechanism of modulating ET A receptor activity.Post-translational modifications of receptors coupled to heterotrimeric guanyl nucleotide-binding proteins (G protein) modulate receptor function and activity (1-3). One such modification is the palmitoylation of conserved cysteine residues located in the cytoplasmic tail of many G protein-coupled receptors. It has been suggested that this acylation provides a membrane anchor that creates a fourth cytoplasmic receptor loop (4, 5). The functional role of palmitoylation has been studied for adrenergic receptors in some detail. Prevention of palmitoylation of a conserved cysteine residue, Cys 341 , of the ␤-adrenergic receptor causes functional uncoupling of the receptor from the adenylyl cyclase pathway (4). Furthermore, the nonpalmitoylated receptor shows an increased basal phosphorylation and a rapid desensitization in response to its ligand (6). Activation of the ␤ 2 -adrenergic receptor results in an enhanced palmitoylation thereby increasing the amount of functionally coupled receptor (7). Adrenergic receptor activation also increases palmitoylation of a receptor-associated stimulatory G protein (8). These findings clearly show the dynamic properties of protein/receptor palmitoylation. Unlike the ␤ 2 -adrenergic receptor a mutation of the corresponding palmitoylation site in the ␣ 2A -adrenergic receptor did not influence the signal transduction activity but decreased the ligand-promoted down-regulation of the receptor (9). On the other hand, purified nonpa...

The evaluation of biological microscopy experiments is a large subfield in image processing. Many methods have been published, which are specially designed for a certain microscopy technique or even for a single experiment. Usually they are evaluated with user annotated data which is prone to errors and, thus, shows inter-and intraobserver variance. We present a simulation software capable to generate micrographs with known ground truth of various microspcopy techniques for an unbiased and objective evaluation.

Dieser Beitrag stellt die Entwicklung eines Industrie 4.0-gerechten Formspannsystems für die Roboterhandhabung vor. Basierend auf einem Flexformmodul wird ein automatisierter Greifer entwickelt, mit dem die Handhabung von dreidimensional freigeformten Bauteilen möglich ist. Dafür wird das bestehende System mit geeigneten Sensoren und Aktoren erweitert. Ziel der Entwicklung ist die kraft- und wegüberwachte Abformung von unbekannten Bauteilen, sodass ohne vorheriges Anlernen des Systems eine vollständige Oberflächennachbildung erfolgt. Mit dem System ist neben der exakten Abformung der Kontur auch die Aufbringung einer definierten Spannkraft möglich.