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Type: Journal article
Title: Huntingtin-associated protein 1 regulates exocytosis, vesicle docking, readily releasable pool size and fusion pore stability in mouse chromaffin cells
Author: Mackenzie, K.
Duffield, M.
Peiris, H.
Phillips, L.
Zanin, M.
Teo, E.
Zhou, X.
Keating, D.
Citation: The Journal of Physiology, 2014; 592(7):1505-1518
Publisher: Wiley
Issue Date: 2014
ISSN: 0022-3751
Statement of
Kimberly D. Mackenzie, Michael D. Duffield, Heshan Peiris, Lucy Phillips, Mark P. Zanin, Ee Hiok Teo, Xin-Fu Zhou and Damien J. Keating
Abstract: Huntingtin-associated protein 1 (HAP1) was initially established as a neuronal binding partner of huntingtin, mutations in which underlie Huntington's disease. Subcellular localization and protein interaction data indicate that HAP1 may be important in vesicle trafficking and cell signalling. In this study, we establish that HAP1 is important in several steps of exocytosis in adrenal chromaffin cells. Using carbon-fibre amperometry, we measured single vesicle exocytosis in chromaffin cells obtained from HAP1(-/-) and HAP1(+/+) littermate mice. Numbers of Ca(2+)-dependent and Ca(2+)-independent full fusion events in HAP1(-/-) cells are significantly decreased compared with those in HAP1(+/+) cells. We observed no change in the frequency of 'kiss-and-run' fusion events or in Ca(2+) entry. Whereas release per full fusion event is unchanged in HAP1(-/-) cells, early fusion pore duration is prolonged, as indicated by the increased duration of pre-spike foot signals. Kiss-and-run events have a shorter duration, indicating opposing roles for HAP1 in the stabilization of the fusion pore during full fusion and transient fusion, respectively. We use electron microscopy to demonstrate a reduction in the number of vesicles docked at the plasma membrane of HAP1(-/-) cells, where membrane capacitance measurements reveal the readily releasable pool of vesicles to be reduced in size. Our study therefore illustrates that HAP1 regulates exocytosis by influencing the morphological docking of vesicles at the plasma membrane, the ability of vesicles to be released rapidly upon stimulation, and the early stages of fusion pore formation.
Keywords: HAP1, huntingtin-associated protein 1;HD,Huntington’s disease; Htt, huntingtin; LDCVs, large dense core vesicles; PSF, pre-spike foot; RRP, readily releasable pool; SAF, stand-alone foot
Description: Article first published online: 17 FEB 2014
Rights: © 2014 The Authors. The Journal of Physiology © 2014 The Physiological Society
RMID: 0030028509
DOI: 10.1113/jphysiol.2013.268342
Appears in Collections:Anatomical Sciences publications

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