Functional Organization of the Porosome Complex and Associated Structures Facilitating Cellular Secretion

Jena, Bhanu P.

doi:10.1152/physiol.00021.2009

Cited by 16 publications

(28 citation statements)

References 111 publications

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“…A mature granule fuses with a unit granule (to grow into a bigger granule) or with the cell's membrane (to exit the cell) via the formation of a circular rosette [11] composed of SNARE proteins [24 -31]. The selfaggregation capacity of the SNARE protein complex has been reported [26][27][28]31,36], whereby each unit granule has a limited number of 'hooks' and the target membranes have a limited number of 'loops'. For example, in SVs, the hook is one t-SNARE (SNAP-25 þ syntaxin complex), the loop is one v-SNARE (VAMP protein), and a SNARE pair is a complex of one t-SNARE and one v-SNARE [28].…”

Section: Quantal Basis Of Vesicle Growth and Information Contentmentioning

confidence: 99%

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Function suggests nano-structure: electrophysiology supports that granule membranes play dice

Hammel

Meilijson

2012

J. R. Soc. Interface.

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Cellular communication depends on membrane fusion mechanisms. SNARE proteins play a fundamental role in all intracellular fusion reactions associated with the life cycle of secretory vesicles, such as vesicle -vesicle and vesicle plasma membrane fusion at the porosome base in the cell plasma membrane. We present growth and elimination (G&E), a birth and death model for the investigation of granule growth, its evoked and spontaneous secretion and their information content. Using a statistical mechanics approach in which SNARE components are viewed as interacting particles, the G&E model provides a simple 'nanomachine' of SNARE self-aggregation behind granule growth and secretion. Results from experimental work, mathematical calculations and statistical modelling suggest that for vesicle growth a minimal aggregation of three SNAREs is required, while for the evoked secretion one SNARE is enough. Furthermore, the required number of SNARE aggregates (which varies between cell types and is nearly proportional to the square root of the mean granule diameter) affects and is statistically identifiable from the size distributions of spontaneous and evoked secreted granules. The new statistical mechanics approach to granule fusion is bound to have a significant changing effect on the investigation of the pathophysiology of secretory mechanisms and methodologies for the investigation of secretion.

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Section: Quantal Basis Of Vesicle Growth and Information Contentmentioning

confidence: 99%

“…Porosomes (or fusion pores), cup-shaped structures measuring only a few nanometres, are the universal secretory machinery in cell membranes of eukaryotic cells. Porosomes contain many different types of protein, especially SNARE proteins, calcium and chloride channels [27,28].…”

Section: Introductionmentioning

confidence: 99%

Function suggests nano-structure: electrophysiology supports that granule membranes play dice

Hammel

Meilijson

2012

J. R. Soc. Interface.

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“…It is natural to think of X, the number of ions located in a small vicinity of the binding protein, as being Poisson-distributed [8,9] with some mean h. From this point of view, secretion rate should be considered to follow the M-K rate relation, whose M-dependence component is rate…”

Section: The M -K Rate Eventmentioning

confidence: 99%

“…The evoked case is generally assumed to be the result of sharply increased Ca 2þ concentration, inducing the exocytosis of most or all granules in the vicinity of the plasma membrane porosome complex [6][7][8][9][10][11][12][13]. Porosomes are permanent cup-shaped lipoprotein structures at the cell plasma membrane [8][9][10], with t-SNAREs at its base. Secretory vesicles transiently dock and .…”

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Function suggests nano-structure: towards a unified theory for secretion rate, a statistical mechanics approach

Hammel

Meilijson

2013

J. R. Soc. Interface.

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The inventory of secretory granules along the plasma membrane can be viewed as maintained in two restricted compartments. The release-ready pool represents docked granules available for an initial stage of fast, immediate secretion, followed by a second stage of granule set-aside secretion pool, with significantly slower rate. Transmission electron microscopy ultrastructural investigations correlated with electrophysiological techniques and mathematical modelling have allowed the categorization of these secretory vesicle compartments, in which vesicles can be in various states of secretory competence. Using the above-mentioned approaches, the kinetics of single vesicle exocytosis can be worked out. The ultra-fast kinetics, explored in this study, represents the immediately available release-ready pool, in which granules bound to the plasma membrane are exocytosed upon Ca .

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Porosomes in uterine epithelial cells: Ultrastructural identification and characterization during early pregnancy

Kalam

Dowland

Lindsay

et al. 2022

Journal of Morphology

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Porosomes are plasma membrane structures in secretory cells that allow transient docking and/or partial fusion of vesicles during which they release their content then disengage. This is referred to as "kiss and run" exocytosis.During early pregnancy, at the time of receptivity, there is a high level of vesicle activity in uterine epithelial cells (UECs). One of the secretory pathways for these vesicles could be via porosomes, which have yet to be identified in UECs.This study identified porosomes in the apical plasma membrane of UECs for the first time. These structures were present on days 1, 5.5, and 6 of early pregnancy, where they likely facilitate partial secretion via "kiss and run" exocytosis. The porosomes were measured and quantified on days 1, 5.5, and 6, which showed there are significantly more porosomes on day 5.5 (receptive) compared to day 1 (nonreceptive) of pregnancy. This increase in porosome numbers may reflect major morphological and molecular changes in the apical plasma membrane at this time such as increased cholesterol and soluble NSF attachment protein receptor proteins, as these are structural and functional components of the porosome complex assembly. Porosomes were observed in both resting (inactive) and dilated (active) states on days 1, 5.5, and 6 of early pregnancy. Porosomes on day 5.5 are significantly more active than on day 1 as demonstrated by the dilation of their base diameter. Further two-way ANOVA analysis of base diameter in resting and dilated states found a significant increase in porosome activity in day 5.5 compared to day 1. This study therefore indicates an increase in the number and activity of porosomes at the time of uterine receptivity in the rat, revealing a mechanism by which the UECs modify the uterine luminal environment at this time.

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Functional Organization of the Porosome Complex and Associated Structures Facilitating Cellular Secretion

Cited by 16 publications

References 111 publications

Function suggests nano-structure: electrophysiology supports that granule membranes play dice

Function suggests nano-structure: electrophysiology supports that granule membranes play dice

Function suggests nano-structure: towards a unified theory for secretion rate, a statistical mechanics approach

Porosomes in uterine epithelial cells: Ultrastructural identification and characterization during early pregnancy

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