Localization of a low Mr GTP-binding protein, rap1 protein, in plasma membranes and secretory granule membranes of rat parotid gland

Yasunaga, Kōjirō; Nagata, Koh‐ichi; Mizuno‐Kamiya, Masako; Yokota, Yutaka; Fujita, Atsushi; Nozawa, Yoshinori

doi:10.1016/0024-3205(94)00882-5

Cited by 9 publications

(6 citation statements)

References 25 publications

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“…However, in contrast to our results, in which we found that the strongest rap1 signal was associated with the SGM, Kameyama et al (1994) found that the strongest rap1 signal was associated with the apical and basolateral PM. These differences may be due to differences in the methods of PM preparation, e.g., Kameyama et al (1994) prepared separate apical and basolateral PM fractions.…”

Section: Discussioncontrasting

confidence: 99%

“…Two-dimensional gel electrophoretic analysis of the SGM, PM, and CY fractions may help to ascertain if they do indeed have identical smgs. Kameyama et al (1994) have reported rap1 localization on the SGM and on both the apical and basolateral PM fractions of the rat parotid gland. However, in contrast to our results, in which we found that the strongest rap1 signal was associated with the SGM, Kameyama et al (1994) found that the strongest rap1 signal was associated with the apical and basolateral PM.…”

Section: Discussionmentioning

confidence: 98%

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Immunolocalization of Rap1 in the Rat Parotid Gland: Detection on Secretory Granule Membranes

D’Silva

DiJulio

Belton

et al. 1997

J Histochem Cytochem.

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WashingtonS U M M A R Y The objective of this study was to localize rap1 in the rat parotid gland. Rap1 is a small GTP-binding protein that has been linked to phagocytosis in neutrophils and various functions in platelets. In this study, we used [ ␣-32 P]-GTP-blot overlay analysis, immunoblot analysis, and immunohistochemistry to identify rap1 in rat parotid gland. The immunohistochemical techniques included immunoperoxidase and widefield microscopy with image deconvolution. Rap1 was identified in the secretory granule membrane (SGM), plasma membrane (PM), and cytosolic (CY) fractions, with the largest signal being in the SGM fraction. The tightly bound vs loosely adherent nature of SGM-associated rap1 was determined using sodium carbonate, and its orientation on whole granules was assessed by trypsin digestion. Rap1 was found to be a tightly bound protein rather than a loosely adherent contaminant protein of the SGM. Its orientation on the cytosolic face of the secretory granule (SG) is of significance in postulating a function for rap1 because exocytosis involves the fusion of the cytoplasmic face of the SG with the cytoplasmic face of the PM, with subsequent release of granule contents (CO). Therefore, the localization and high concentration of rap1 on the SGM and its cytosolic orientation suggest that it may play a role in the regulation of secretion.

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Section: Discussioncontrasting

confidence: 99%

Section: Discussionmentioning

confidence: 98%

Immunolocalization of Rap1 in the Rat Parotid Gland: Detection on Secretory Granule Membranes

D’Silva

DiJulio

Belton

et al. 1997

J Histochem Cytochem.

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“…Rap proteins are divided into two subgroups, Rap1 and Rap2. Rap1 has been identified in the secretory granule membrane, plasma membrane and cytosol of rat parotid acinar cells (Kameyama et al , 1994; D'Silva et al , 1997) and has been observed to translocate to the cytosol following β‐adrenergic receptor activation (D'Silva et al , 1998).…”

Section: Salivary Protein Secretionmentioning

confidence: 99%

Understanding salivary fluid and protein secretion

2002

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“…Rap1 has been identified on secretory granule membranes in mouse and rat pancreatic acini by mass spectrometry and immunocytochemistry (15,100) as well as in rat parotid glands (18,57). In addition, two Rap1-GEFs have recently been found in mouse pancreatic acini, CalDAG-GEFIII and Epac1 (100).…”

Section: Small G Proteins On Secretory Granulesmentioning

confidence: 98%

Small G proteins as key regulators of pancreatic digestive enzyme secretion

Williams

Chen

Sabbatini

2009

American Journal of Physiology-Endocrinology and Metabolism

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Small GTP-binding (G) proteins act as molecular switches to regulate a number of cellular processes, including vesicular transport. Emerging evidence indicates that small G proteins regulate a number of steps in the secretion of pancreatic acinar cells. Diverse small G proteins have been localized at discrete compartments along the secretory pathway and particularly on the secretory granule. Rab3D, Rab27B, and Rap1 are present on the granule membrane and play a role in the steps leading up to exocytosis. Whether the function of these G proteins is simply to ensure appropriate targeting or if they are involved as regulatory molecules is discussed. Most evidence suggests that Rab3D and Rab27B play a role in tethering the secretory granule to its target membrane. Other Rabs have been identified on the secretory granule that are associated with different steps in the secretory pathway. The Rho family small G proteins RhoA and Rac1 also regulate secretion through remodeling of the actin cytoskeleton. Possible mechanisms for regulation of these G proteins and their effector molecules are considered.

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Localization of a low Mr GTP-binding protein, rap1 protein, in plasma membranes and secretory granule membranes of rat parotid gland

Cited by 9 publications

References 25 publications

Immunolocalization of Rap1 in the Rat Parotid Gland: Detection on Secretory Granule Membranes

Immunolocalization of Rap1 in the Rat Parotid Gland: Detection on Secretory Granule Membranes

Understanding salivary fluid and protein secretion

Small G proteins as key regulators of pancreatic digestive enzyme secretion

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