1) Describe Wnt signaling pathway. 2) Give 2 examples of effector proteins and d
ID: 59222 • Letter: 1
Question
1) Describe Wnt signaling pathway. 2) Give 2 examples of effector proteins and describe. 3) Give 5 examples of what turns off the signal in cell signaling and describe each briefly. 4) How phosphyralation promote and inhibit signaling? 1) Describe Wnt signaling pathway. 2) Give 2 examples of effector proteins and describe. 3) Give 5 examples of what turns off the signal in cell signaling and describe each briefly. 4) How phosphyralation promote and inhibit signaling? 1) Describe Wnt signaling pathway. 2) Give 2 examples of effector proteins and describe. 3) Give 5 examples of what turns off the signal in cell signaling and describe each briefly. 4) How phosphyralation promote and inhibit signaling?Explanation / Answer
1) Describe Wnt signaling pathway.
The Wnt signaling pathway is a conserved pathway in metazoan animals. The name Wnt is resultant from a fusion of the name of the Drosophila segment polarity gene wingless and the name of the vertebrate homolog, integrated or int-1. The extra-cellular Wnt signal stimulates several intra-cellular signal transduction cascades, including the canonical or Wnt/-catenin dependent pathway and the non-canonical or -catenin-independent pathway which can be divided into the Planar Cell Polarity pathway and the Wnt/Ca2+ pathway.
Wnt proteins regulate a dizzying array of cellular processes including cell fate determination, motility, polarity, primary axis formation and organogenesis and most recently, this pathway has been implicated in stem cell renewal. As the signaling pathways that play crucial role during embryogenesis are tightly regulated, the expression of the Wnt proteins and Wnt antagonists are exquisitely restricted both temporally and spatially during development. Deregulated Wnt signaling has catastrophic consequences for the developing embryo and it is now well appreciated that defective Wnt signaling is a causative factor for a number of pleiotropic human pathologies. Most notably, these pathologies include cancers of the breast, colon and skin, skeletal defects and human birth defect disorders including the most common human neural tube closure birth; spina bifida.
2) Give 2 examples of effector proteins and describe.
Non-genetic classes of regulatory proteins include those target, effector proteins that are involved in special cellular functions such as signaling as receptor proteins and pumps, adhesion, chemotaxis, cellular transport and active transport, and metabolic regulation, including enzymatic action and protein degradation. Effector molecules bring about regulation by binding other molecules, and genetic effector molecules can participate in the regulation of gene expression. Modulator molecules bind to a regulatory sites during allosteric modulation, where effectors act as activators or inhibitors. (Allosteric proteins have an active (catalytic) site and an allosteric (effector) site.) Effector proteins such as cGMP,GAP, GTPase activating protein regulate the activity of other proteins.
3) Give 5 examples of what turns off the signal in cell signaling and describe each briefly.
Signal-transduction cascades mediate the sensing and processing of stimuli. These molecular circuits detect, amplify, and integrate diverse external signals to generate responses such as changes in enzyme activity, gene expression, or ion-channel activity.
Protein phosphatases are one mechanism for the termination of a signaling process.
GTPase-Activating Proteins, or GAPs, or GTPase-Accelerating Proteins are a family of regulatory proteins whose members can bind to activated G proteins and stimulate their GTPase activity, with the result of terminating the signaling event.
Signal turn-off includes removal of Ca++ from the cytosol by action of Ca++-ATPase pumps, and degradation of IP3.
AKAPs localize signal cascades within a cell. They coordinate activation of protein kinases as well as rapid turn-off of signals.
4) How phosphyralation promote and inhibit signaling?
Protein phosphorylation is a common means of information transfer. Many second messengers elicit responses by activating protein kinases. These enzymes transfer phosphoryl groups from ATP to specific serine, threonine, and tyrosine residues in proteins.
Protein phosphatases are enzymes that hydrolytically remove specific phosphoryl groups from modified proteins. Phosphatases are in cells, where they catalyze reactions that remove phosphate groups from proteins. When hormone stimulation of a receptor ends, phosphatases dephosphorylate enough components of the phosphorylation cascade that the response slows and stops.
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