Lysosomal Calcium Channels in Autophagy and Cancer

Ca2+ is pivotal intracellular messenger that coordinates multiple cell functions such as fertilization, growth, differentiation, and viability. Intracellular Ca2+ signaling is regulated by both extracellular Ca2+ entry and Ca2+ release from intracellular stores. Apart from working as the cellular recycling center, the lysosome has been increasingly recognized as a significant intracellular Ca2+ store that provides Ca2+ to regulate many cellular processes. The lysosome also talks to other organelles by releasing and taking up Ca2+. In lysosomal Ca2+-dependent processes, autophagy is particularly important, because it has been implicated in many human diseases including cancer. This review will discuss the major components of lysosomal Ca2+ stores and their roles in autophagy and human cancer progression.

Actin Cytoskeleton as Actor in Upstream and Downstream of Calcium Signaling in Plant Cells

In plant cells, calcium (Ca2+) serves as a versatile intracellular messenger, participating in several fundamental and important biological processes. Recent studies have shown that the actin cytoskeleton is not only an upstream regulator of Ca2+ signaling, but also a downstream regulator. Ca2+ has been shown to regulates actin dynamics and rearrangements via different mechanisms in plants, and on this basis, the upstream signaling encoded within the Ca2+ transient can be decoded. Moreover, actin dynamics have also been proposed to act as an upstream of Ca2+, adjust Ca2+ oscillations, and establish cytosolic Ca2+ ([Ca2+]cyt) gradients in plant cells. In the current review, we focus on the advances in uncovering the relationship between the actin cytoskeleton and calcium in plant cells and summarize our current understanding of this relationship.

Thinking through acidic Ca2+ stores

Glutamate signaling regulates neuronal activity and synaptic plasticity, which underlies learning and memory. In this issue of Science Signaling, Foster et al. found that metabotropic glutamate receptors mediate long-term potentiation in hippocampal neurons by mobilizing acidic endolysosomal Ca2+ stores through the intracellular messenger NAADP.

Principles of Signal Transduction

Chapter 4 covers postreceptor intracellular messenger cascades through which neurotransmitters and neurotrophic factors, and their receptors, produce their diverse physiological effects. A major advance over the past generation of research has been an appreciation of the complex webs of intracellular signaling pathways that control every aspect of a neuron’s functioning, from neurotransmitter signaling to cell shape and motility to gene expression. While only a small number of medications used in psychiatry today have as their initial target intracellular signaling proteins, it is likely that drug development efforts will look increasingly to such proteins for the discovery of novel medications with fundamentally new mechanisms of action.