Signaling and receptor-mediated endocytosis

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PROBLEM

Receptors are involved in receptor-mediated endocytosis (eg LDL receptors, vitellogenin receptors). Are these signaling receptors, if all they are doing is resulting in endocytosis of the ligand? Is this any different to a transporter moving its substrate, or an enzyme recognizing its substrate?

For a summary of the problems, see slides 61-64 in the following presentation from the February 2011 signaling workshop.


BACKGROUND

Wikipedia



RELATED SOURCEFORGE ITEM

Tanya's SF item suggests splitting the receptors into those that signal and those that endocytose their substrate:

https://sourceforge.net/tracker/?func=detail&aid=2894756&group_id=36855&atid=440764


PROPOSAL

-I think we are agreed that RME is not a signaling event, and that the first step doesn't count as signal transduction.

-Internalization of the ligand (and/or receptor) can of course regulate a signaling event as it regulates how much ligand or receptor is available for signaling.


Restricting 'receptor activity ; GO:0004872' to those receptors that signal [2] will create the split of signaling receptors and 'other receptors'.

Q: Do we want a generic 'receptor activity' term in MF? If so, how would it be defined other than 'binding'?

 molecular_function
 --%receptor activity ; GO:NEW
 ----%signaling receptor activity ; GO:0004872
 ----%receptor activity involved in endocytosis ; GO:NEW
 ------%lipoprotein particle receptor activity ; GO:0030228
 ------%vitellogenin receptor activity ; GO:0008196
 
 receptor activity ; GO:NEW
 Combining with an extracellular or intracellular molecule or signal to initiate a change in cell activity.
 signaling receptor activity ; GO:0004872
 Combining with a signal to initiate a change in cell activity. A signal is any variable property or parameter that serves to convey information, and may be a physical entity such as a gene product or small molecule, a photon, or a change in state such as movement or voltage change.
 is_a: signal transducer activity
 synonym: receptor involved in signal transduction
 
 receptor activity involved in endocytosis ; GO:NEW
 Combining with a extracellular molecule on the surface of the cell and acting to internalize the molecule.
 part_of: receptor-mediated endocytosis ; GO:0006898
 synonym: endocytotic receptor activity