Ruled by waves? Intracellular and intercellular calcium signalling

Abstract

The field of calcium signalling has evolved rapidly the last 20 years. Physiologists had worked with cytosolic Ca2+ as the coupler of excitation and contraction of muscles and as a secretory signal in exocrine glands and in the synapses of the brain for several decades before the discovery of cellular calcium as a second messenger. Development of powerful techniques for measuring the concentration of cytosolic free calcium ions in cell suspensions and later in single cells and even in different cellular compartments, has resulted in an upsurge in the knowledge of the cellular machinery involved in intracellular calcium signalling. However, the focus on intracellular mechanisms might have led this field of study away from physiology. During the last few years there is an increasing evidence for an important role of calcium also as an intercellular signal. Via gap junctions calcium is able to co-ordinate cell populations and even organs like the liver. Here we will give an overview of the general mechanisms of intracellular calcium signalling, and then review the recent data on intercellular calcium signals. A functional coupling of cells in different tissues and organs by the way of calcium might be an important mechanism for controlling and synchronizing physiological responses

Enhanced spontaneous Ca2+ events in endothelial cells reflect signalling through myoendothelial gap junctions in pressurized mesenteric arteries

“…As PE and KCl each had a similar effect on spontaneous Ca 2+ events in the endothelium, Ca 2+ rather than IP 3 may be expected to be the predominant influence diffusing from the smooth muscle to the endothelial cells. Ca 2+ and IP 3 are, however, interdependent in terms of their regenerative process [54]. Indeed, the ability of KCl to evoke rises in endothelial cell Ca 2+ appears dependent on phospholipase C and IP 3 -induced Ca 2+ release [37], supporting an important role for this signalling pathway in rat mesenteric arteries.…”

“…The exact contribution possible by Ca 2+ and IP 3 passing through gap junctions remains to be defined. Generally, PE acts to increase IP 3 and thus release Ca 2+ from the sarcoplasmic reticulum, while KCl increases Ca 2+ via depolarization and the opening of smooth muscle voltage-gated Ca 2+ channels [53,54]. As PE and KCl each had a similar effect on spontaneous Ca 2+ events in the endothelium, Ca 2+ rather than IP 3 may be expected to be the predominant influence diffusing from the smooth muscle to the endothelial cells.…”

Regulation of oscillation dynamics in biochemical systems with dual negative feedback loops

“…Oscillations are ubiquitously observed in cells and have been shown to play important roles in a broad array of cellular processes [45,46]. The oscillatory behaviour produced can be time-dependent, as in glycolytic oscillations [47], the circadian rhythms [48], the cell cycles [49], or space-dependent, as in calcium waves [50,51] and neuronal oscillations [52]. In all of these examples, oscillations are driven by some sort of negative-feedback mechanism.…”

Regulation of intracellular calcium levels by polyunsaturated fatty acids, arachidonic acid and docosahexaenoic acid, in astrocytes: possible involvement of phospholipase A2

“…Functional coupling of cells in different tissues and organs by way of Ca 2+ is an important mechanism for controlling and synchronizing physiological responses (for review, see [39]). During the last few years, a great amount of evidence has been accumulated to demonstrate an active role of astrocytes in the physiology of the nervous system as dynamic regulatory elements in neurotransmission.…”