Mitochondria Structure and Position in the Local Control of Calcium Signals in Smooth Muscle Cells

This chapter describes how the structure and positioning of mitochondria contribute to the control of Ca²⁺ signaling, including a previously unrecognized ability of the position of the organelles to increase local Ca²⁺ entry via voltage-dependent Ca²⁺ channels. In native smooth muscle cells, mitochondria contribute to the localization of Ca²⁺ signals and to the modulation of the amplitude of Ca²⁺ signals. In smooth muscle, mitochondria control contractility, proliferation, and growth through regulation of cytoplasmic Ca²⁺ concentrations. The precise structure and position of mitochondria have been studied most extensively in cultured smooth muscle cells because of the relative ease that the organelles can be visualized in these cells. Live cell imaging is required to appreciate the precise relationship between position and structure of mitochondria and the control of Ca²⁺ signaling in fully-differentiated cells. Features of Ca²⁺ signals including the amplitude, duration, frequency and location are encoded by various physiological stimuli.