Stable Golgi-Mitochondria Complexes and Formation of Golgi Ca2+ Gradients in Pancreatic Acinar Cells

We have determined the localization of the Golgi with respect to other organelles in living pancreatic acinar cells and the importance of this localization to the establishment of Ca2+ gradients over the Golgi. Using confocal microscopy and the Golgi-specific fluorescent probe 6-((N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino)hexanoyl)sphingosine, we found Golgi structures localizing to the outer edge of the secretory granular region of individual acinar cells. We also assessed Golgi positioning in acinar cells located within intact pancreatic tissue using two-photon microscopy and found a similar localization. The mitochondria segregate the Golgi from lateral regions of the plasma membrane, the nucleus, and the basal part of the cytoplasm. The Golgi is therefore placed between the principal Ca2+ release sites in the apical region of the cell and the important Ca2+ sink formed by the peri-granular mitochondria. During acetylcholine-induced cytosolic Ca2+ signals in the apical region, large Ca2+ gradients form over the Golgi (decreasing from trans- to cis-Golgi). We further describe a novel, close interaction of the peri-granular mitochondria and the Golgi apparatus. The mitochondria and the Golgi structures form very close contacts, and these contacts remain stable over time. When the cell is forced to swell, the Golgi and mitochondria remain juxtaposed up to the point of cell lysis. The strategic position of the Golgi (closer to release sites than the bulk of the mitochondrial belt) makes this organelle receptive to local apical Ca2+ transients. In addition the Golgi is ideally placed to be preferentially supplied by ATP from adjacent mitochondria. We have determined the localization of the Golgi with respect to other organelles in living pancreatic acinar cells and the importance of this localization to the establishment of Ca2+ gradients over the Golgi. Using confocal microscopy and the Golgi-specific fluorescent probe 6-((N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino)hexanoyl)sphingosine, we found Golgi structures localizing to the outer edge of the secretory granular region of individual acinar cells. We also assessed Golgi positioning in acinar cells located within intact pancreatic tissue using two-photon microscopy and found a similar localization. The mitochondria segregate the Golgi from lateral regions of the plasma membrane, the nucleus, and the basal part of the cytoplasm. The Golgi is therefore placed between the principal Ca2+ release sites in the apical region of the cell and the important Ca2+ sink formed by the peri-granular mitochondria. During acetylcholine-induced cytosolic Ca2+ signals in the apical region, large Ca2+ gradients form over the Golgi (decreasing from trans- to cis-Golgi). We further describe a novel, close interaction of the peri-granular mitochondria and the Golgi apparatus. The mitochondria and the Golgi structures form very close contacts, and these contacts remain stable over time. When the cell is forced to swell, the Golgi and mitochondria remain juxtaposed up to the point of cell lysis. The strategic position of the Golgi (closer to release sites than the bulk of the mitochondrial belt) makes this organelle receptive to local apical Ca2+ transients. In addition the Golgi is ideally placed to be preferentially supplied by ATP from adjacent mitochondria. The pancreatic acinar cell is the classical model for studies of the secretory pathway. In the pancreatic acinar cell, Palade (1Palade G.E. Science. 1975; 189: 347-358Crossref PubMed Scopus (2313) Google Scholar) first described the segregation, transport, and discharge of secretory proteins. Ca2+ regulates processing of secretory proteins within (2Corbett E.F. Michalak M. Trends Biochem. Sci. 2000; 25: 307-311Abstract Full Text Full Text PDF PubMed Scopus (219) Google Scholar) and transport along the secretory pathway (3Ivessa N.E. de-Lemos-Chiarandini C. Gravotto D. Sabatini D.D. Kreibich G. J. Biol. Chem. 1995; 270: 25960-25967Abstract Full Text Full Text PDF PubMed Scopus (63) Google Scholar, 4Porat A. Elazar Z. J. Biol. Chem. 2000; 275: 29233-29237Abstract Full Text Full Text PDF PubMed Scopus (76) Google Scholar, 5Ahluwalia J.P. Topp J.D. Weirather K. Zimmermann M. Stamnes M. J. Biol. Chem. 2001; 276: 34148-34155Abstract Full Text Full Text PDF PubMed Scopus (44) Google Scholar). In turn many of the membrane-bound compartments of the secretory pathway serve as a source and a sink for Ca2+ (6Pozzan T. Rizzuto R. Volpe P. Meldolesi J. Physiol. Rev. 1994; 74: 595-636Crossref PubMed Scopus (30) Google Scholar, 7Thomas A.P. Bird G.S. Hajnoczky G. Robb-Gaspers L.D. Putney Jr., J.W. FASEB J. 1996; 10: 1505-1517Crossref PubMed Scopus (416) Google Scholar, 8Ashby M.C. Tepikin A.V. Physiol. Rev. 2002; 82: 701-734Crossref PubMed Scopus (101) Google Scholar, 9Berridge M.J. Bootman M.D. Roderick H.L. Nat. Rev. Mol. Cell. Biol. 2003; 4: 517-529Crossref PubMed Scopus (4065) Google Scholar). Ca2+ signaling and the secretory pathway are inextricably tied in pancreatic acinar cells (10Williams J.A. Annu. Rev. Physiol. 2001; 63: 77-97Crossref PubMed Scopus (188) Google Scholar). Structural and functional polarity is an important aspect of this reciprocal relationship (11Bolender R.P. J. Cell Biol. 1974; 6: 269-287Crossref Scopus (204) Google Scholar, 12Meldolesi J. Castiglioni G. Parma R. Nassivera N. De Camilli P. J. Cell Biol. 1978; 79: 156-172Crossref PubMed Scopus (138) Google Scholar, 13Petersen O.H. Burdakov D. Tepikin A.V. BioEssays. 1999; 21: 851-860Crossref PubMed Scopus (75) Google Scholar). Initiation of the secretory pathway occurs at the basolateral part of the cell with protein synthesis and terminates with Ca2+-dependent secretion at the apical membrane (14Jamieson J.D. Palade G.E. J. Cell Biol. 1971; 50: 135-158Crossref PubMed Scopus (259) Google Scholar, 15Nemoto T. Kimura R. Ito K. Tachikawa A. Miyashita Y. Lino M. Kasai H. Nat. Cell Biol. 2001; 3: 253-259Crossref PubMed Scopus (147) Google Scholar, 16Thorn P. Fogarty K.E. Parker I. Proc. Natl. Acad. Sci. U. S. A. 2004; 101: 6774-6779Crossref PubMed Scopus (100) Google Scholar). The endoplasmic reticulum (ER) 1The abbreviations used are: ER, endoplasmic reticulum; ACh, acetylcholine; SG, secretory granule; NBD C6-ceramide, 6-((N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino)hexanoyl)sphingosine. 1The abbreviations used are: ER, endoplasmic reticulum; ACh, acetylcholine; SG, secretory granule; NBD C6-ceramide, 6-((N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino)hexanoyl)sphingosine. and nucleus are located in the basolateral part of the cell, whereas the secretory granules (SGs) are located in the apical pole (1Palade G.E. Science. 1975; 189: 347-358Crossref PubMed Scopus (2313) Google Scholar, 11Bolender R.P. J. Cell Biol. 1974; 6: 269-287Crossref Scopus (204) Google Scholar, 17Gerasimenko O.V. Gerasimenko J.V. Rizzuto R.R. Treiman M. Tepikin A.V. Petersen O.H. Cell Calcium. 2002; 32: 261-268Crossref PubMed Scopus (46) Google Scholar). The most striking polarization is that of the mitochondria with three distinct groupings: peri-granular, sub-plasmalemmal, and peri-nuclear (18Tinel H. Cancela J.M. Mogami H. Gerasimenko J.V. Gerasimenko O.V. Tepikin A.V. Petersen O.H. EMBO J. 1999; 18: 4999-5008Crossref PubMed Scopus (313) Google Scholar, 19Straub S.V. Giovannucci D.R. Yule D.I. J. Gen. Physiol. 2000; 116: 547-559Crossref PubMed Scopus (159) Google Scholar, 20Park M.K. Ashby M.C. Erdemli G. Petersen O.H. Tepikin A.V. EMBO J. 2001; 20: 1863-1874Crossref PubMed Scopus (266) Google Scholar, 21Collins T.J. Bootman M.D. J. Exp. Biol. 2003; 206: 1993-2000Crossref PubMed Scopus (93) Google Scholar, 22Johnson P.R. Dolman N.J. Pope M. Vaillant C. Petersen O.H. Tepikin A.V. Erdemli G. Cell Tissue Res. 2003; 313: 37-45Crossref PubMed Scopus (42) Google Scholar). In this study we examined the localization of the Golgi with respect to other cellular organelles and the functional consequences of this localization. We found close Golgi-mitochondria contacts that remain remarkably stable over time and during different cellular perturbations. Finally, we visualized Ca2+ gradients that are formed over the Golgi as a consequence of relative positioning of the Golgi and mitochondria. Pancreatic Acinar Cell Preparation—Pancreata were obtained from male CD 1 mice (21–30 days old) as previously described (23Thorn P. Lawrie A.M. Smith P.M. Gallacher D.V. Petersen O.H. Cell. 1993; 74: 661-668Abstract Full Text PDF PubMed Scopus (422) Google Scholar) in accordance with the Animals (Scientific Procedures) Act, 1986. Undissociated tissue was immobilized and imaged as previously described (24Ashby M.C. Camello-Almarez C. Geras Petersen O.H. Tepikin A.V. J. Biol. Chem. 2003; 278: 20860-20864Abstract Full Text Full Text PDF PubMed Scopus (42) Google Scholar). Single cells and clusters of acinar cells were obtained by brief (10-min) collagenase digestion of the pancreas, followed by gentle agitation with a pipette. For all experiments, isolated cells, pancreatic clusters, or pancreata were suspended in a standard HEPES-buffered physiological salt solution containing 140 mm NaCl, 4.7 mm KCL, 1.13 mm MgCl2,10 mm HEPES, 10 mm glucose, 1 mm CaCl2, pH adjusted to 7.2 (with NaOH). In studies of Ca2+ signaling, cells were stimulated by pressure application of acetylcholine (ACh) (see below). Confocal Microscopy—Live cells were examined on a Leica TCS SP2 or Leica SP2-AOBS confocal microscope with a 63× water immersion objective lens and a 1.2 NA. SGs were visualized using confocal reflectance (excitation, 543 nm; emission, 538–548 nm). To visualize the Golgi, cells were loaded with 2.5 μm NBD C6-ceramide for 15 min at 4 °C. NBD C6-ceramide was excited by a 476 nm laser line, and emission was collected at 500–550 nm. Cells were loaded with 50 nm MitoTracker Deep Red for 15 min at 37 °C to visualize mitochondria. MitoTracker Deep Red was excited with a 633 nm laser line, and emission was collected above 650 nm. For ER labeling, cells were incubated with 500 nm BODIPY Texas Red thapsigargin for 15 min at room temperature and excited at 594 nm, and the emission was collected between 600 and 650 nm. Images of intracellular organelles were obtained with a confocal pinhole corresponding to 1 Airy unit. The Ca2+ -sensitive indicator Fura Red was loaded into the cells in the membrane-permeant AM form (5 μm for 30 min at room temperature) and imaged using a 488 nm laser line for excitation and 570–650 nm for emission. Applications of agonists and analysis to calculate cytosolic Ca2+ gradients were performed as described by Gerasimenko et al. (25Gerasimenko O.V. Gerasimenko J.V. Petersen O.H. Tepikin A.V. Pflugers Arch. 1996; 432: 1055-1061Crossref PubMed Scopus (55) Google Scholar). Briefly, ACh stimulation of pancreatic acinar cells was via a pipette filled with a 100 μm ACh solution. The pipette was attached to a pressure injection system (Eppendorf, Hamburg, Germany); this system allowed short (0.1–1-s) applications of ACh. In some experiments local Ca2+ signals were produced by stimulation with a low (10 nm) concentration of ACh. The formation of Ca2+ gradients across the cells axis with respect to the Golgi was analyzed in the following way: cells in which ACh elicited apically localized Ca2+ signal were selected for analysis. Line profiles of Fura Red fluorescence were taken across the cell from the apical to basolateral pole; the signal was then averaged for six such selected lines. The profile at rest was then subtracted from the stimulated profile (during peak of Ca2+ transient) giving rise to the ΔF (change in fluorescence) profile reflecting Ca2+ changes along the apical to basolateral axis. This trace was then compared with the distribution of NBD C6-ceramide fluorescence recorded along the same line. Chemicals—All fluorescent dyes were obtained from Molecular Probes (Eugene, OR). All other chemicals were from Sigma. Localization of the Golgi and Its Interaction with the Perigranular Mitochondrial Belt—Labeling of the Golgi using the Golgi-specific probe NBD C6-ceramide (26Pagano R.E. Martin O.C. Kang H.C. Haugland R.P. J. Cell Biol. 1991; 113: 1267-1279Crossref PubMed Scopus (399) Google Scholar) in live cells reveals a large crescent-shaped organelle also located in the peri-granular part of the cell (Fig. 1A, I and II; supplemental Fig. S1; supplemental Video 1). A similar localization of the Golgi has been described previously (using immunofluorescence labeling) in fixed isolated pancreatic acinar cells (27Shin D.M. Zhao X.S. Zeng W. Mozhayeva M. Muallem S. J. Cell Biol. 2000; 150: 1101-1112Crossref PubMed Scopus (76) Google Scholar, 28Thomas D.D.H. Weng N. Groblewski G.E. Am. J. Physiol. 2004; 287: G253-G263Crossref PubMed Scopus (20) Google Scholar). Using two-photon microscopy, we also investigated the positioning of the Golgi in cells located within intact (undissociated) pancreatic tissue or large pancreatic clusters and found a clearly resolved crescent-shaped organelle located in the peri-granular region (see supplemental Fig. S1). We were able to disassemble this structure by incubating the cells for 30 min with brefeldin A (5 μg/ml; n supplemental Fig. a to disassemble the Golgi J. Cell. Full Text PDF PubMed Scopus Google Scholar). studies have a of mitochondria the SGs in pancreatic acinar cells (18Tinel H. Cancela J.M. Mogami H. Gerasimenko J.V. Gerasimenko O.V. Tepikin A.V. Petersen O.H. EMBO J. 1999; 18: 4999-5008Crossref PubMed Scopus (313) Google Scholar, 19Straub S.V. Giovannucci D.R. Yule D.I. J. Gen. Physiol. 2000; 116: 547-559Crossref PubMed Scopus (159) Google Scholar, 20Park M.K. Ashby M.C. Erdemli G. Petersen O.H. Tepikin A.V. EMBO J. 2001; 20: 1863-1874Crossref PubMed Scopus (266) Google Scholar, 21Collins T.J. Bootman M.D. J. Exp. Biol. 2003; 206: 1993-2000Crossref PubMed Scopus (93) Google Scholar, 22Johnson P.R. Dolman N.J. Pope M. Vaillant C. Petersen O.H. Tepikin A.V. Erdemli G. Cell Tissue Res. 2003; 313: 37-45Crossref PubMed Scopus (42) Google Scholar). of the Golgi in this region a of the organelles and to relative of acinar cells with NBD C6-ceramide (Fig. 1A, and MitoTracker Deep Red (Fig. 1A, that these organelles are juxtaposed and (Fig. 1A, The peri-granular mitochondrial is on the basolateral of the Golgi (Fig. 1A, of of this part reveals that the Golgi (Fig. has close contacts with the mitochondria from the peri-granular (Fig. and In the regions of contacts, the between these organelles is that is the of confocal microscopy (Fig. the membrane from the ER to the Golgi and on the Golgi (1Palade G.E. Science. 1975; 189: 347-358Crossref PubMed Scopus (2313) Google Scholar) be by the close of the Golgi to the mitochondria. The membrane also on Ca2+ signals A. Elazar Z. J. Biol. Chem. 2000; 275: 29233-29237Abstract Full Text Full Text PDF PubMed Scopus (76) Google Scholar) and Ca2+ gradients J.P. Topp J.D. Weirather K. Zimmermann M. Stamnes M. J. Biol. Chem. 2001; 276: 34148-34155Abstract Full Text Full Text PDF PubMed Scopus (44) Google Scholar). Localization of the Golgi on the apical of the mitochondrial the Golgi to Ca2+ in this cell by physiological of 8Ashby M.C. Tepikin A.V. Physiol. Rev. 2002; 82: 701-734Crossref PubMed Scopus (101) Google Scholar, P. Lawrie A.M. Smith P.M. Gallacher D.V. Petersen O.H. Cell. 1993; 74: 661-668Abstract Full Text PDF PubMed Scopus (422) Google Scholar, and H. Miyashita Y. Cell. 1993; 74: Full Text PDF PubMed Scopus Google also Golgi Localization and Ca2+ below). of Golgi and mitochondria positioning be in a region adjacent to the apical part of the lateral plasma The line in Fig. the lateral is that the mitochondria (Fig. the Golgi (Fig. up to the of the lateral membrane (Fig. and supplemental Video peri-granular mitochondria (Fig. the edge of the Golgi (Fig. of the distribution of the organelles (Fig. with the of mitochondrial Ca2+ that the lateral mitochondria by the Golgi are the mitochondria that in the Ca2+ M.K. Ashby M.C. Erdemli G. Petersen O.H. Tepikin A.V. EMBO J. 2001; 20: 1863-1874Crossref PubMed Scopus (266) Google Scholar). The region adjacent to the apical part of the lateral membrane was to in K. D.M. Muallem S. Cell. 2003; PubMed Scopus Google the lateral mitochondria be important in the signaling in this part the The and Cell many cell mitochondria form a R. P. W. Fogarty K.E. T. Science. PubMed Scopus Google Scholar, Biochem. 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We used confocal recorded over time to the of these close contacts formed between Golgi and mitochondria. of mitochondria and Golgi were recorded over time and changes in cell and some of the the regions in which into close stable over time (Fig. A and of changes in contacts were during short stimulation with of 10 μm ACh supplemental Fig. or nm To further the of Golgi-mitochondria contacts we of the cells by the solution with water (Fig. and The Golgi structures to be in close with mitochondria up to the point of cell (Fig. the time point to the cell by in the of the n During the cell up to the time of cell the Golgi and mitochondria from with regions of close contacts cell in the mitochondria most of and from the Golgi and other organelles of Golgi and in Pancreatic Acinar the relative positioning of intracellular in this cell the Golgi is adjacent to the nucleus (Fig. The which a basal than the Golgi a between the Golgi and the nucleus (Fig. A and The bulk of the ER is found with respect to the Golgi and the mitochondria (Fig. the of the ER described previously O.V. Gerasimenko J.V. Rizzuto R.R. Treiman M. Tepikin A.V. Petersen O.H. Cell Calcium. 2002; 32: 261-268Crossref PubMed Scopus (46) Google Scholar, M.K. Petersen O.H. Tepikin A.V. EMBO J. 2000; PubMed Scopus Google Scholar) be in the apical (with respect to part of the cells (Fig. ER for the apical Ca2+ release from the ER M.K. Petersen O.H. Tepikin A.V. EMBO J. 2000; PubMed Scopus Google Scholar, H. K. Tepikin A.V. Petersen O.H. Cell. Full Text Full Text PDF PubMed Scopus Google Scholar). The Golgi the whereas the peri-granular mitochondrial the Golgi (Fig. from the basal and lateral This in the Golgi a position in the of the SGs on the apical (with respect to the of the part of the cell (Fig. The Ca2+ from the ER in the secretory (Fig. therefore first the Golgi the bulk of the mitochondria into and this Ca2+ via mitochondrial R. M. T. PubMed Scopus Google Scholar, G. Robb-Gaspers L.D. A.P. Cell. 1995; 82: Full Text PDF PubMed Scopus Google Scholar). We to this by Ca2+ gradients during localized apical Ca2+ signals with respect to the position of the Golgi. The Golgi Localization and Ca2+ NBD C6-ceramide and the Fura we imaged apically Ca2+ signals with respect to the Golgi localization (Fig. The of the cell is in Fig. The apical and basal regions of for Ca2+ are in Fig. I. The line along which the Ca2+ was is also on the (Fig. The Golgi be on Fig. Fig. an apically Ca2+ signal by pressure application of ACh The the time used for the of the Ca2+ The between and stimulated were and are in Fig. I the line the whereas the Golgi fluorescence profile along the same line is on Fig. the Ca2+ along a line across the cell (Fig. the stimulation and at the time of Ca2+ we the Ca2+ gradients across the Golgi We found that during Ca2+ signaling (23Thorn P. Lawrie A.M. Smith P.M. Gallacher D.V. Petersen O.H. Cell. 1993; 74: 661-668Abstract Full Text PDF PubMed Scopus (422) Google Scholar, H. Miyashita Y. Cell. 1993; 74: Full Text PDF PubMed Scopus Google the Golgi is to Ca2+ gradients that μm the Golgi (Fig. For in experiments, we the Golgi and mitochondria (Fig. and similar line profiles as used in Fig. to the localization of the Golgi and mitochondria The mitochondrial profile with the Golgi, most of the mitochondrial was found within a region the Golgi. of Ca2+ by these mitochondria M.K. Ashby M.C. Erdemli G. Petersen O.H. Tepikin A.V. EMBO J. 2001; 20: 1863-1874Crossref PubMed Scopus (266) Google Scholar) for the of the Ca2+ the Golgi. The that mitochondrial Ca2+ a in local Ca2+ signals and formation of Ca2+ gradients is by in which of mitochondria with the or an of the transport a of and in of local Ca2+ signaling to Ca2+ (18Tinel H. Cancela J.M. Mogami H. Gerasimenko J.V. Gerasimenko O.V. Tepikin A.V. Petersen O.H. EMBO J. 1999; 18: 4999-5008Crossref PubMed Scopus (313) Google Scholar). et al. S.V. Giovannucci D.R. Yule D.I. J. Gen. Physiol. 2000; 116: 547-559Crossref PubMed Scopus (159) Google Scholar) that of mitochondria with 4 in of Ca2+ by were obtained using an of the mitochondrial P.R. Tepikin A.V. Erdemli G. Cell Calcium. 2002; 32: PubMed Scopus Google Scholar). of mitochondrial Ca2+ M.K. Ashby M.C. Erdemli G. Petersen O.H. Tepikin A.V. EMBO J. 2001; 20: 1863-1874Crossref PubMed Scopus (266) Google Scholar) and in during brief Ca2+ S. T. P.R. Erdemli G. Petersen O.H. Tepikin A.V. J. Physiol. 2002; Scopus Google Scholar) also the of mitochondria. In study we experiments with of mitochondria by a of and (with for Golgi and of We the and were able to the formation of Ca2+ signals in the peri-granular, and basal regions Fig. n an of these experiments is that the position of the mitochondria is by which is clearly to the the Golgi is between the Ca2+ source sites in the apical and the Ca2+ sink Ca2+ gradients are formed over this organelle with the Ca2+ concentration over the than that over the in pancreatic acinar cells, the Golgi is to in cytosolic Ca2+ and to Ca2+ the Golgi were on the basolateral of the peri-granular mitochondrial be to Ca2+ gradients during local Ca2+ the peri-granular mitochondrial from the Ca2+ the of mitochondria (with respect to the of Ca2+ signal and in of the Golgi, this cell has to Ca2+ signaling in the Golgi have also been to in other of in mitochondria Ca2+ signaling A.M. A. J. Gen. Physiol. 2003; PubMed Scopus Google whereas in acinar cells mitochondria the nucleus, Ca2+ and an important in of ATP for Giovannucci D.R. G. T.J. Yule D.I. J. Biol. Chem. 2004; Full Text Full Text PDF PubMed Scopus (75) Google Scholar). positioning of the Golgi with respect to such mitochondrial be a of an The relative positioning of the Golgi and mitochondria in pancreatic acinar cells functional polarity within the peri-granular mitochondrial The from the ER to the Golgi and the Golgi compartments (1Palade G.E. Science. 1975; 189: 347-358Crossref PubMed Scopus (2313) Google Scholar) be by ATP of the close of mitochondria to these (Fig. 1). to the in other cells between the ER and mitochondria R. P. W. Fogarty K.E. T. Science. PubMed Scopus Google Scholar, G. Hajnoczky G. Cell Calcium. 2001; PubMed Scopus Google close contacts between the Golgi and mitochondria between these is important to that mitochondria on the basal of the mitochondrial in pancreatic acinar cells are by and in close to ER P.R. Dolman N.J. Pope M. Vaillant C. Petersen O.H. Tepikin A.V. Erdemli G. Cell Tissue Res. 2003; 313: 37-45Crossref PubMed Scopus (42) Google Scholar). a of positioning of close contacts be formed by mitochondria and other cellular organelles local ATP the of the contacts is for mitochondria are by the Golgi (Fig. and are therefore to Ca2+ signals in the apical part of the cell M.K. Ashby M.C. Erdemli G. Petersen O.H. Tepikin A.V. EMBO J. 2001; 20: 1863-1874Crossref PubMed Scopus (266) Google Scholar). The Golgi also serve as a functional containing and of Ca2+ P. T. Rizzuto R. EMBO J. PubMed Scopus Google Scholar, J. De H. K. G. Cell Calcium. 2004; PubMed Scopus (46) Google Scholar). The Golgi therefore has the to from Ca2+ signals also to these signals as a Ca2+ sink or as the of the Ca2+ The positioning of the Golgi in of the mitochondrial with signaling Ca2+ and which are for secretory processing (2Corbett E.F. Michalak M. Trends Biochem. Sci. 2000; 25: 307-311Abstract Full Text Full Text PDF PubMed Scopus (219) Google Scholar) and (3Ivessa N.E. de-Lemos-Chiarandini C. Gravotto D. Sabatini D.D. Kreibich G. J. Biol. Chem. 1995; 270: 25960-25967Abstract Full Text Full Text PDF PubMed Scopus (63) Google Scholar, 4Porat A. Elazar Z. J. Biol. Chem. 2000; 275: 29233-29237Abstract Full Text Full Text PDF PubMed Scopus (76) Google Scholar, 5Ahluwalia J.P. Topp J.D. Weirather K. Zimmermann M. Stamnes M. J. Biol. Chem. 2001; 276: 34148-34155Abstract Full Text Full Text PDF PubMed Scopus (44) Google Scholar). In study we found that the cytosolic Ca2+ gradients of along the line from the apical to the basal part of the acinar cell (25Gerasimenko O.V. Gerasimenko J.V. Petersen O.H. Tepikin A.V. Pflugers Arch. 1996; 432: 1055-1061Crossref PubMed Scopus (55) Google in the we found that these cytosolic Ca2+ signals the Golgi and within the peri-granular mitochondrial into the nucleus and the rest of the basal We and for We also and Rizzuto for with