Membrane trafficking produces distinct beta‐adrenergic signaling for Cl secretion and K secretion in guinea pig distal colonic mucosa

Abstract

Epinephrine (epi) activated Cl and K secretion (sec) in isolated mucosa from guinea pig distal colon, measured as short‐circuit current. These components of the response were distinguished by inhibition of Cl sec with a β2 antagonist (ICI‐118551) that spared K sec; propranolol inhibited both. Interfering with endocytosis prolonged the transient Cl sec and inhibited sustained K sec. Both the dynamin inhibitor dynasore and the clathrin‐coated‐pit blocker mono‐dansylcadaverine produced this response. Dynasore also inhibited the sustained epi‐induced increase in mucosal cAMP, while leaving the transient cAMP increase intact. Manipulating the ubiquitylation cycle by inhibiting ubiquitin‐E1 ligase (UBEI‐41, BioGenova) also prolonged the epi‐induced Cl sec transient and slowed the onset of K sec. Conversely, inhibiting deubiquitylases (PR‐619, LifeSensors) alone stimulated K sec, while blunting Cl sec and producing a non‐additive increase in K sec with epi. Disruption of the actin (latrunculin B, cytochalasin D) and microtubule (nocodazole) cytoskeleton inhibited epi‐induced K sec without altering Cl sec. Together these results support an activation process involving internalization of β2‐adrenergic receptors that terminates signaling for Cl sec, and β‐adrenergic stimulation of K sec that requires receptor internalization prior to activation of the sustained cAMP signaling cascades. [NIH DK65845]