PKCδ and pharmacomechanical control of cerebral arterial tone

From coupling mechanisms to spatial toneCerebral resistance arteries regulate not only the amount of blood delivered to the brain, but also its regional distribution.This distinction matters because neural activity and metabolic demand vary between brain regions and change over time.A mechanism that produces uniform tone along an artery might help to control overall flow, but it cannot fully describe the sharply localised changes in perfusion.Arterial smooth muscle contracts through two related but distinct coupling processes.During electromechanical coupling, membrane depolarisation opens L-type Ca 2+ channels, increases cytosolic Ca 2+ and activates myosin light chain kinase.Pharmacomechanical coupling can increase force without a corresponding change in membrane potential, mainly by reducing myosin light chain phosphatase (MLCP) activity, thereby increasing Ca 2+ sensitisation.MLCP contains the catalytic PP1c subunit and the targeting subunit MYPT1.Two established signalling routes converge on this phosphatase: PKC-dependent phosphorylation of CPI-17 and RhoA/Rho-kinase-dependent phosphorylation of MYPT1 (Somlyo & Somlyo, 2003).Previous work in mouse mesenteric arteries introduced the concept of functional bias, in which the balance between electromechanical and pharmacomechanical coupling varies with agonist concentration and the size of the stimulated region (Haghbin et al., 2024).The focus article extends this idea to cerebral arteries and asks whether a