PMC

Secretory pathways in parotid acinar cells. The main organelles of the secretory pathway are labeled. TGN, trans-Golgi network; IM, immature secretory granule; SG, mature secretory granules; CL, constitutive-like secretory vesicle; mR, minor regulated pathway vesicle. The vesicular transport pathways discussed in the text are indicated by numbered arrows: (1) major regulated secretory pathway, (2) minor regulated secretory pathway, (3) apical constitutive secretory pathway, (4) constitutive-like secretory pathway, (5) basolateral constitutive secretory pathway, (6) basolateral secretion of secretory granules, and (7) alternate basolateral constitutive secretory pathway.

Cross-dimerization with ChEL. A, 293 cells were transiently transfected with empty vector or plasmids to express secretory ChEL-Myc (ChEL) or secretory FLAG-NL1, -NL2, -NL3, or -NL4. Transfected cells were pulse-labeled for 30 min with ³⁵S-amino acids and chased for either 5 h (upper panel, a time when ChEL secretion has gone to completion) or 24 h (lower panel, a time when neuroligin secretion has gone to completion). The cells were lysed, and both cells and media were immunoprecipitated with anti-Myc (for ChEL) and anti-FLAG (for neuroligins). B, the left panel shows 293 cells co-transfected with plasmids expressing secretory ChEL-Myc and either empty vector (Con) or secretory FLAG-NL1, -NL2, -NL3, or -NL4. Cell lysates were immunoprecipitated (IP) with α-Myc antibody, resolved by SDS-PAGE and immunoblotted (WB) with anti-FLAG antibody. The right panel shows 293 cells co-transfected with plasmids expressing secretory ChEL and either empty vector (Con) or AChE-Myc (AChE). The cells were lysed in the presence of 1 mm dithiobis(succinimidyl propionate) cross-linker, immunoprecipitated (IP) with α-Tg antibody, resolved by SDS-PAGE and immunoblotted (WB) with anti-Myc antibody. C, the left panel shows 293 cells co-transfected as in the left panel of B, or transfected with empty vector (Con). The right panel shows 293 cells co-transfected with plasmids expressing secretory ChEL-HA plus secretory FLAG-NL3, or secretory FLAG-NL3 alone, or transfected with empty vector (Con). Media were collected from transfected cells for 24 h; the upper left panel shows the comparable expression of secretory ChEL partner in each sample; the upper right panel shows comparable expression of the secretory NL3 partner. Media were immunoprecipitated (IP) with α-Myc (lower left) or anti-HA (lower right); the immunoprecipitates were resolved by SDS-PAGE and immunoblotted (WB) with anti-FLAG antibodies. D, cells were transfected to either singly express secretory FLAG-NL3, singly express secretory ChEL-HA, or co-express both constructs, or neither. After 24 h, the cells were lysed and the media were collected; samples were analyzed by Western blotting with anti-FLAG antibodies.

Histochemistry of the sole and side foot (sections are oriented to the bottom for the sole foot and to the right for the side foot, according their natural location) of Haliotis tuberculata. (a) and (b) HID/AB. The sole (a) and side (b) secretory cells in dark containing sulphated acidic glycoconjugates, moreover some subepithelial glands (a, arrows) and side secretory cells (b) stain in blue revealing the presence of carboxylated acidic glycoconjugates. Both glycoconjugates are present in a few secretory cells (b, arrow). Bar: 200 μm (a), 100 μm (b) (c) and (d). PAS. Presence of neutral glycoconjugates in the sole secretory cells and subepithelial gland (c), and the side secretory cells (d) Bar: 200 μm (c), 100 μm (d) (e) UEA I (fucose). The subepithelial glands are strongly reactive to the lectin, and a few secretory cells (arrow) are also positive. Biotinylated lectin, counterstained with hematoxylin. Bar: 100 μm. (f) and (g) AAA (fucose). Some side secretory cells show positivity (f) which increases after desulphation (g) Lectin labeled with digoxigenin. Bar: 100 μm. H. Con A (mannose). The apical portion of the sole epithelial cells and subepithelial gland exhibit reactivity to mannose. Biotinylated lectin, counterstained with hematoxylin. Bar: 50 μm. (i) GNA (mannose). After desulphation GNA binds to some side secretory cells. Lectin labeled with digoxigenin. Bar: 50 μm. (j), and (k) PNA (Galactose beta 1-3 N-acetyl-galactosamine). After desulphation the number of side secretory cells increases (j) and a few sole secretory cells appear (k) Lectin labeled with digoxigenin. Bar: 50 μm. (l) and (m) WGA (N-acetyl-glucosamine). The weak reaction changes after desulphation, increasing intensity and number of sole (l) and side (m) secretory cells. Subepithelial glands appear weakly stained (l). Biotinylated lectin. Bar: 100 μm (l), 50 μm (m) (n), and (o) DBA (N-acetyl-galactosamine). The number of positive side secretory cells increases after desulphation (n) and a high number sole secretory cells appear (o) Bar: 50 μm.

Marginal of the leaf blade EFN (A). Petiolar EFN (B-G, I). Abaxial surface of leaf blade EFN (H). A. P. incarnata, note exudate in the subcuticular space and nuclei centralized in secretory epidermal cell. B. P. suberosa with short secretory epidermal cells. C. P. incarnata with elongated secretory epidermal cells and secretory parenchyma with flattened cells, note the vascular bundle ending with phloem cells (arrow). D. P. eichleriana, elongated secretory epidermal cells and secretory parenchyma with flattened cells. E. P. racemosa showing elongated secretory epidermal cells, note regions with two layers of cells (arrow). F. P. deidamioides, showing distinctive secretory parenchyma cells and subsecretory parenchyma with vascular bundles. G. P. haematostigma with unicellular trichome and extensions of the subepidermal parenchyma (arrow). H. Multicellular trichome in P. coccinea. I. P. gabana with elongated secretory epidermal cells and vascular bundles ending with phloem cells in the subsecretory parenchyma. Ep = epidermis; Sp = secretory parenchyma.