Ca2+-independent fusion of secretory granules with phospholipase A2-treated plasma membranes <i>in vitro</i>

Nagao, Tsuneatsu; Kubo, Taeko; Fujimoto, Ritsuko; Nishio, Hideaki; Takeuchi, Tadayoshi; Hata, Fumiaki

doi:10.1042/bj3070563

Cited by 35 publications

(24 citation statements)

References 53 publications

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“…The contribution of this phospholipase A 2 to amylase secretion from rat parotid acini (57) and to insulin secretion by pancreatic ␤ cells (58) has also been reported. This is consistent with the fact that calcium is not required for the fusion of secretory granules with the plasma membrane (59). Additionally, the presence of an iPLA 2 on the membrane of rat parotid secretory granules has been reported (60).…”

Section: Discussionsupporting

confidence: 71%

Activation by P2X7 Agonists of Two Phospholipases A2 (PLA2) in Ductal Cells of Rat Submandibular Gland

Alzola¹,

Pérez-Etxebarria²,

Kabré³

et al. 1998

Journal of Biological Chemistry

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]AA in response to the purinergic agonists was still observed; this response was not affected by AACOCF 3 and completely blocked by bromoenol lactone. ATP and Bz-ATP stimulated a calcium-independent secretion of kallikrein, which could be blocked by BEL but which was enhanced by AACOCF 3 . It is concluded that the P2X 7 receptor in ductal cells is coupled to kallikrein secretion through a calcium-dependent cPLA 2 and a calcium-independent iPLA 2 .ATP plays an important role as an extracellular agonist that mediates its various effects by acting on specific membrane P2 receptor subtypes (1, 2). P2 receptors comprise receptors of the ligand-gated ion channel type, as well as of the G-proteinlinked superfamily, termed P2X and P2Y, respectively (3). At present, seven genes for P2X receptors have been cloned (4 -8), but their physiological significance has not been fully established yet. One of the most recently cloned P2X receptors (the P2X 7 ) has a pharmacological profile typical of the receptor previously termed P 2Z (9) with the photoactivable analog of ATP, Bz-ATP, 1 the most potent agonist. The P 2Z receptor induces the formation of pores when exposed to concentrations of extracellular ATP in the 100 M to 1 mM range (Refs. 10 -12, but see also Ref. 13). In contrast to other P2X receptors, the P2X 7 receptor has a long COOH-terminal intracellular chain, which is by itself not responsible for the lytic properties of this receptor (14) but probably induces the formation of a second messenger involved in the lysis (12). In summary, the P2X 7 (P 2Z )-receptors share with the other P2X receptors the ability to open a non-selective channel and with P 2Z receptors the induction of cell lysis by repeated applications of the agonist (8).Since the pioneering work of Gallacher (15), ATP has been recognized as a major non-adrenergic non-cholinergic stimulus of saliva secretion. Salivation, like other exocrine secretions, occurs in two steps; (a) acinar cells secrete an isotonic plasmalike fluid, and (b) the electrolyte composition of this primary secretion is modified during its transfer to the mouth by the ductal tree (16). The ducts reabsorb Na ϩ and Cl Ϫ and secrete K ϩ and HCO 3 Ϫ (17). The study of these two phases of the secretory process has been facilitated by the description of an improved technique to separate ducts and acini (18). It could be observed that extracellular ATP increased the intracellular

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Section: Discussionsupporting

confidence: 71%

Activation by P2X7 Agonists of Two Phospholipases A2 (PLA2) in Ductal Cells of Rat Submandibular Gland

Alzola¹,

Pérez-Etxebarria²,

Kabré³

et al. 1998

Journal of Biological Chemistry

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“…Activation of cPLA 2 due to accumulations in intracellular Ca 2+ may then serve to maintain insulin secretion and inhibition of cPLA 2 appears to reduce secretion only 50% ( 233 ). The role of sPLA 2 may reside in its ability to enhance the ability of plasma membranes to bind secretory granules ( 238,(240)(241)(242), though a role for sPLA 2 in inactivating the K ATP channels has also been described ( 237 ). In view of expression of membrane receptors for sPLA 2 in ␤ -cells ( 238,243,244 ), the role of sPLA 2 s in ␤ -cells may be to serve as feedback modulators to maintain/amplify insulin secretion.…”

Section: +mentioning

confidence: 99%

Calcium-independent phospholipases A2 and their roles in biological processes and diseases

Ramanadham

Ali

Ashley

et al. 2015

Journal of Lipid Research

161

176

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The Ca 2+ -independent phospholipases A 2 (iPLA 2 s) are part of a diverse family of PLA 2 s that hydrolyze the sn -2 substituent from membrane phospholipids to release a free fatty acid and a lysolipid ( 1, 2 ). These enzymes are ubiquitously expressed, and in contrast to secretory PLA 2 s (sPLA 2 s) and cytosolic PLA 2 s (cPLA 2 s), do not require Ca 2+ for either translocation or activity. Some of the fi rst descriptions of iPLA 2 activity were in the mid-to late-1980s with the identifi cation of a plasmalogen-selective PLA 2 in Abstract Among the family of phospholipases A 2 (PLA 2 s) are the Ca 2+ -independent PLA 2 s (iPLA 2 s) and they are designated group VI iPLA 2 s. In relation to secretory and cytosolic PLA 2 s, the iPLA 2 s are more recently described and details of their expression and roles in biological functions are rapidly emerging. The iPLA 2 s or patatin-like phospholipases (PNPLAs) are intracellular enzymes that do not require Ca 2+ for activity, and contain lipase (GXSXG) and nucleotide-binding (GXGXXG) consensus sequences. Though nine PNPLAs have been recognized, PNPLA8 (membraneassociated iPLA 2 ␥ ) and PNPLA9 (cytosol-associated iPLA 2 ␤ ) are the most widely studied and understood. The iPLA 2 s manifest a variety of activities in addition to phospholipase, are ubiquitously expressed, and participate in a multitude of biological processes, including fat catabolism, cell differentiation, maintenance of mitochondrial integrity, phospholipid remodeling, cell proliferation, signal transduction, and cell death. As might be expected, increased or decreased expression of iPLA 2 s can have profound effects on the metabolic state, CNS function, cardiovascular performance, and cell survival; therefore, dysregulation of iPLA 2 s can be a critical factor in the development of many diseases. This review is aimed at providing a general framework of the current understanding of the iPLA 2 s and discussion of the potential mechanisms of action of the iPLA 2 s and related involved lipid mediators. -Ramanadham, S

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“…PGF2a synthesis can be inhibited by pertussis toxin (135), indicating a second level of control. The residual lysophosphatidylcholine has been implicated in exocytosis (136,137), suggesting a mechanism by which stretch could trigger release of growth factors.…”

Section: Phospholipasesmentioning

confidence: 99%

Mechanotransduction in skeletal muscle

Burkholder¹

2007

Front Biosci

105

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Mechanical signals are critical to the development and maintenance of skeletal muscle, but the mechanisms that convert these shape changes to biochemical signals is not known. When a deformation is imposed on a muscle, changes in cellular and molecular conformations link the mechanical forces with biochemical signals, and the close integration of mechanical signals with electrical, metabolic, and hormonal signaling may disguise the aspect of the response that is specific to the mechanical forces. The mechanically induced conformational change may directly activate downstream signaling and may trigger messenger systems to activate signaling indirectly. Major effectors of mechanotransduction include the ubiquitous mitogen activated protein kinase (MAP) and phosphatidylinositol-3' kinase (PI-3K), which have well described receptor dependent cascades, but the chain of events leading from mechanical stimulation to biochemical cascade is not clear. This review will discuss the mechanics of biological deformation, loading of cellular and molecular structures, and some of the principal signaling mechanisms associated with mechanotransduction. KeywordsSkeletal muscle; mechanotransduction; stretch INTRODUCTIONThe detection and response to physical forces is essential to all cells, but is particularly relevant to those that play a fundamentally mechanical role. The primordial nature of the cellular interaction with the physical world suggests that its control should be highly regulated and specific, and that the response should integrate many aspects of cellular physiology. Pathways involved in detecting and producing forces in muscle overlap those involved in detecting nutrient availability (1,2), intracellular energy status (3,4), and oxidative status (5,6). The signaling pathways modulated by force, insulin and insulin-like growth factor I (IGF-I)(7), adenosine monophosphate (AMP) dependent kinase (AMPK) (8), reactive oxygen species (ROS) (9), and prostaglandins (PG) (10) seem intractably intertwined.The adaptations of skeletal muscle to mechanical signals have been widely described, and the interested reader is referred to several recent reviews (11)(12)(13)(14). The physiological increase in force generating capacity associated with activity, and the increase in flexibility associated with stretch, were recognized in antiquity, but the mechanisms by which those changes manifest are still unclear. The present intention is to consider the shape changes and forces associated with mechanical signals and juxtapose them with observed changes in biochemical signaling to determine what might contribute to the cellular perception of mechanical signals.Careful consideration of the mechanical environment is the first step to sort out that labyrinth of signaling. When one considers mechanisms by which the mechanical environment can be NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript sensed, it is common to think of "force" and "deformation" separately. Sometimes this distinction is legitimate, bu...

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Ca2+-independent fusion of secretory granules with phospholipase A2-treated plasma membranes in vitro

Cited by 35 publications

References 53 publications

Activation by P2X7 Agonists of Two Phospholipases A2 (PLA2) in Ductal Cells of Rat Submandibular Gland

Activation by P2X7 Agonists of Two Phospholipases A2 (PLA2) in Ductal Cells of Rat Submandibular Gland

Calcium-independent phospholipases A2 and their roles in biological processes and diseases

Mechanotransduction in skeletal muscle

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