Multiple cytosolic calcium buffers in posterior pituitary nerve terminals

The Journal of General Physiology
Shane M McMahonMeyer B Jackson

Abstract

Cytosolic Ca(2+) buffers bind to a large fraction of Ca(2+) as it enters a cell, shaping Ca(2+) signals both spatially and temporally. In this way, cytosolic Ca(2+) buffers regulate excitation-secretion coupling and short-term plasticity of release. The posterior pituitary is composed of peptidergic nerve terminals, which release oxytocin and vasopressin in response to Ca(2+) entry. Secretion of these hormones exhibits a complex dependence on the frequency and pattern of electrical activity, and the role of cytosolic Ca(2+) buffers in controlling pituitary Ca(2+) signaling is poorly understood. Here, cytosolic Ca(2+) buffers were studied with two-photon imaging in patch-clamped nerve terminals of the rat posterior pituitary. Fluorescence of the Ca(2+) indicator fluo-8 revealed stepwise increases in free Ca(2+) after a series of brief depolarizing pulses in rapid succession. These Ca(2+) increments grew larger as free Ca(2+) rose to saturate the cytosolic buffers and reduce the availability of Ca(2+) binding sites. These titration data revealed two endogenous buffers. All nerve terminals contained a buffer with a Kd of 1.5-4.7 µM, and approximately half contained an additional higher-affinity buffer with a Kd of 340 nM. Western ...Continue Reading

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Citations

Jan 10, 2020·Journal of Neuroendocrinology·Jeffrey G TaskerWilliam E Amstrong
Jul 19, 2017·The Journal of Eukaryotic Microbiology·Helmut Plattner
Oct 6, 2018·Trends in Neurosciences·Shane M McMahon, Meyer B Jackson

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Methods Mentioned

BETA
Fluorescence
dissection

Software Mentioned

R ( R Development Core Team
pClamp8
Origin

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