signaling gradients

CELL BIOLOGY: ON THE ORCHESTRATION OF THE MITOTIC SPINDLE: "The concept of signaling gradients is a familiar one in animal development[3]. Release of a diffusible and slowly degraded chemical, or morphogen, from a specific site can produce an extracellular concentration gradient that provides positional information to cells. The effect on a particular cell (for example, inducing differentiation) is determined by the cell's threshold in the response to the graded signal. If there are multiple thresholds, then the gradient can produce patterns of different cell responses. These may be limited to precise concentrations of the morphogen, and hence a precise position within a developing tissue. Intracellular gradients that provide positional cues can be generated through subcellular localization of mRNA, such as the localization of bicoid mRNA at the anterior pole of the Drosophila oocyte. Local translation subsequently produces a gradient of bicoid morphogen during early development[4]."

Mechanism For Degradation Of G Proteins

UCSD Researchers Determine Mechanism For Degradation Of G Proteins: "G proteins regulate everything from hormone secretion to the beating of the heart.
The researchers found that GIPN appears to specifically target G proteins for degradation and thereby regulates G protein signaling by controlling the amount of G protein expressed in the cell. This occurs via GIPN binding to the N terminus of G alpha interacting proteins (GAIP), which is the mechanism that sets the ubiquitin system in motion.
The ubiquitin system is used extensively by the cell for the turnover and degradation of proteins in both the cytoplasm, the material surrounding the nucleus, and in cell membranes. Ubiquitin, itself, is a small peptide tag that marks a protein for destruction. The interaction of GIPN and GAIP, which was also discovered by the UCSD team, is part of the machinery that places the little ubiquitin tag on a protein."