Apocrine secretion in Drosophila salivary glands: subcellular origin, dynamics, and identification of secretory proteins

• Published in: PloS one 2014-04, Vol.9 (4), p.e94383-e94383
• Main Authors: Farkaš, Robert, Ďatková, Zuzana, Mentelová, Lucia, Löw, Péter, Beňová-Liszeková, Denisa, Beňo, Milan, Sass, Miklós, Řehulka, Pavel, Řehulková, Helena, Raška, Otakar, Kováčik, Lubomír, Šmigová, Jana, Raška, Ivan, Mechler, Bernard M
• Format: Article
• Language: English
• Subjects: Actin; Analysis; Animals; Apocrine Glands - metabolism; Apocrine Glands - ultrastructure; Apoptosis; Biology and Life Sciences; Cell death; Cellular biology; Cytoskeleton; Deoxyribonucleic acid; DNA; DNA - metabolism; Drosophila; Drosophila melanogaster; Drosophila melanogaster - metabolism; Drosophila Proteins - metabolism; Endocrinology; Exocytosis; Fluorescent Dyes - metabolism; Genetic aspects; Genetics; Glands; Insects; Laboratories; Larva - growth & development; Larva - metabolism; Medicine; Mitochondria; Muscle proteins; Muscles; Myosin; Nucleoli; Pathology; Physiological aspects; Protein Biosynthesis; Protein synthesis; Proteins; Proteomics; Pupa - metabolism; Pyruvic acid; Recombinant Fusion Proteins - metabolism; Research and Analysis Methods; Salivary gland; Salivary glands; Salivary Glands - metabolism; Salivary Glands - ultrastructure; Salivary Proteins and Peptides - metabolism; Subcellular Fractions - metabolism; Transcription, Genetic; Tubulin; Tumor suppressor genes; Western blotting
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0094383

In contrast to the well defined mechanism of merocrine exocytosis, the mechanism of apocrine secretion, which was first described over 180 years ago, remains relatively uncharacterized. We identified apocrine secretory activity in the late prepupal salivary glands of Drosophila melanogaster just prior to the execution of programmed cell death (PCD). The excellent genetic tools available in Drosophila provide an opportunity to dissect for the first time the molecular and mechanistic aspects of this process. A prerequisite for such an analysis is to have pivotal immunohistochemical, ultrastructural, biochemical and proteomic data that fully characterize the process. Here we present data showing that the Drosophila salivary glands release all kinds of cellular proteins by an apocrine mechanism including cytoskeletal, cytosolic, mitochondrial, nuclear and nucleolar components. Surprisingly, the apocrine release of these proteins displays a temporal pattern with the sequential release of some proteins (e.g. transcription factor BR-C, tumor suppressor p127, cytoskeletal β-tubulin, non-muscle myosin) earlier than others (e.g. filamentous actin, nuclear lamin, mitochondrial pyruvate dehydrogenase). Although the apocrine release of proteins takes place just prior to the execution of an apoptotic program, the nuclear DNA is never released. Western blotting indicates that the secreted proteins remain undegraded in the lumen. Following apocrine secretion, the salivary gland cells remain quite vital, as they retain highly active transcriptional and protein synthetic activity.