title: Phosphatidic acid induces ligand-independent epidermal growth factor receptor endocytic traffic through PDE4 activation.
abstract: Endocytosis modulates EGFR function by compartmentalizing and attenuating or enhancing its ligand-induced signaling. Here we show that it can also control the cell surface versus intracellular distribution of empty/inactive EGFR. Our previous observation that PKA inhibitors induce EGFR internalization prompted us to test phosphatidic acid (PA) generated by phospholipase D (PLD) as an endogenous down-regulator of PKA activity, which activates rolipram-sensitive type 4 phosphodiesterases (PDE4) that degrade cAMP. We found that inhibition of PA hydrolysis by propranolol, in the absence of ligand, provokes internalization of inactive (neither tyrosine-phosphorylated nor ubiquitinated) EGFR, accompanied by a transient increase in PA levels and PDE4s activity. This EGFR internalization is mimicked by PA micelles and is strongly counteracted by PLD2 silencing, rolipram or forskolin treatment, and PKA overexpression. Accelerated EGFR endocytosis seems to be mediated by clathrin-dependent and -independent pathways, leading to receptor accumulation in juxtanuclear recycling endosomes, also due to a decreased recycling. Internalized EGFR can remain intracellular without degradation for several hours or return rapidly to the cell surface upon discontinuation of the stimulus. This novel regulatory mechanism of EGFR, also novel function of signaling PA, can transmodulate receptor accessibility in response to heterologous stimuli.
authors.affiliation: Departamento de Inmunología Clínica y Reumatología, Facultad de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile.
authors.forename: Andrés
authors.initials: A
authors.lastname: Norambuena
authors.forename: Claudia
authors.initials: C
authors.lastname: Metz
authors.forename: Juan E
authors.initials: JE
authors.lastname: Jung
authors.forename: Antonia
authors.initials: A
authors.lastname: Silva
authors.forename: Carolina
authors.initials: C
authors.lastname: Otero
authors.forename: Jorge
authors.initials: J
authors.lastname: Cancino
authors.forename: Claudio
authors.initials: C
authors.lastname: Retamal
authors.forename: Juan C
authors.initials: JC
authors.lastname: Valenzuela
authors.forename: Andrea
authors.initials: A
authors.lastname: Soza
authors.forename: Alfonso
authors.initials: A
authors.lastname: González
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D002966:Clathrin / Q000378:metabolism; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D054703:Cyclic Nucleotide Phosphodiesterases, Type 4 / Q000235:genetics / Q000378:metabolism*; D004705:Endocytosis; D011992:Endosomes / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D066246:ErbB Receptors / Q000235:genetics / Q000378:metabolism*; D005434:Flow Cytometry; D006367:HeLa Cells; D006801:Humans; D006868:Hydrolysis / Q000187:drug effects; D015151:Immunoblotting; D051379:Mice; D041681:NIH 3T3 Cells; D010712:Phosphatidic Acids / Q000378:metabolism*; D010739:Phospholipase D / Q000235:genetics / Q000378:metabolism; D011433:Propranolol / Q000494:pharmacology; D034622:RNA Interference; D020889:Rolipram / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D000319:Adrenergic beta-Antagonists; D002966:Clathrin; D010712:Phosphatidic Acids; D005576:Colforsin; D011433:Propranolol; D000242:Cyclic AMP; D066246:ErbB Receptors; D017868:Cyclic AMP-Dependent Protein Kinases; C105606:phospholipase D2; D054703:Cyclic Nucleotide Phosphodiesterases, Type 4; D010739:Phospholipase D; D020889:Rolipram