Calcium goes nuclear

Afine reticulum that pokes its fingers across the nucleus is capable of storing and releasing calcium, according to Wihelma Echevarría, Michael Nathanson (Yale University, New Haven, CT), and colleagues. The physiological activators of the compartment remain obscure, but they could potentially induce localized signaling in the nucleus.

Intranuclear extensions of the ER have been described previously, but the Yale group is the first to show that the compartment both contains and can release calcium. Localized photorelease of inositol 1,4,5-trisphosphate (InsP₃) in the nucleus resulted in a gradient of calcium that spread from the site of photorelease across the nucleus. The effects of nuclear calcium release were distinct from those of cytosolic calcium release: nuclear calcium caused translocation of a labeled protein kinase C (PKC)...