Role in Presence and Absence of Hedgehog Signaling
Patched is part of a negative feedback mechanism for Hedgehog signaling that helps shape the spatial gradient of signaling activity across tissues. In the absence of hedgehog, low levels of patched are sufficient to suppress activity of the signal transduction pathway. When Hedgehog is present and binds to Patched, Patched somehow inhibits the activity of Smoothened, a G protein-coupled receptor, most of which is stored in membrane bound vesicles internally within the cell and which increases at the cell surface when Hedgehog is present. Smoothened must be present on the cell membrane in order for the Hedgehog signaling pathway to be activated. Among other genes, the transcription of the patched gene is induced by Hedgehog signaling, with the accumulation of the Patched protein limiting signaling through the Smoothened protein. Recent work implicates the cilium in intracellular trafficking of Hedgehog signaling components in vertebrate cells.
Read more about this topic: Patched
Famous quotes containing the words role in, role, presence and/or absence:
“Certainly parents play a crucial role in the lives of individuals who are intellectually gifted or creatively talented. But this role is not one of active instruction, of teaching children skills,... rather, it is support and encouragement parents give children and the intellectual climate that they create in the home which seem to be the critical factors.”
—David Elkind (20th century)
“This [new] period of parenting is an intense one. Never will we know such responsibility, such productive and hard work, such potential for isolation in the caretaking role and such intimacy and close involvement in the growth and development of another human being.”
—Joan Sheingold Ditzion and Dennie Palmer (20th century)
“There have been heroes for whom this world seemed expressly prepared, as if creation had at last succeeded; whose daily life was the stuff of which our dreams are made, and whose presence enhanced the beauty and ampleness of Nature herself.”
—Henry David Thoreau (1817–1862)
“... in no part of the world is genteel visiting founded on esteem, in the absence of suitable furniture and complete dinner-service.”
—George Eliot [Mary Ann (or Marian)