PKCs pick through Ca²⁺

Calcium signals destined for mitochondria are first screened by protein kinase C (PKC) isoforms, according to Pinton et al., on page 223. Different PKCs then adjust the organelles' responses to their liking.

PKC is a Ca²⁺-activated kinase that comes in many flavors. Pinton et al. analyzed the contribution of several of these flavors to Ca²⁺ signaling by overexpressing or inhibiting individual isoforms in cells. Their effects were assessed by stimulating cells with an extracellular agonist to elicit Ca²⁺ stores from the ER into the cytoplasm.

One flavor, PKCα, limited all Ca²⁺ signaling by dampening this ER release. Others, however, worked specifically at the mitochondria. PKCζ increased mitochondrial Ca²⁺ uptake, whereas PKCβ and δ reduced it. Thus, activation of PKC upon initial...