Salivary Gland Proteins Research Articles

Toward a catalog for the transcripts and proteins (sialome) from the salivary gland of the malaria vector Anopheles gambiae.

Hundreds of Anopheles gambiae salivary gland cDNA library clones have been sequenced. A cluster analysis based on sequence similarity at e(-60) grouped the 691 sequences into 251 different clusters that code for proteins with putative secretory, housekeeping, or unknown functions. Among the housekeeping cDNAs, we found sequences predicted to code for novel thioredoxin, tetraspanin, hemopexin, heat shock protein, and TRIO and MBF proteins. Among secreted cDNAs, we found 21 novel A. gambiae salivary sequences including those predicted to encode amylase, calreticulin, selenoprotein, mucin-like protein and 30-kDa allergen, in addition to antigen 5- and D7-related proteins, three novel salivary gland (SG)-like proteins and eight unique putative secreted proteins (Hypothetical Proteins, HP). The electronic version of this paper contains hyperlinks to FASTA-formatted files for each cluster with the best match to the nonredundant (NR) and conserved domain databases (CDD) in addition to CLUSTAL alignments of each cluster. The N terminus of 12 proteins (SG-1, SG-1-like 2, SG-6, HP 8, HP 9-like, 5' nucleotidase, 30-kDa protein, antigen 5- and four D7-related proteins) has been identified by Edman degradation of PVDF-transferred, SDS/PAGE-separated salivary gland proteins. Therefore, we contribute to the generation of a catalog of A. gambiae salivary transcripts and proteins. These data are freely available and will eventually become an invaluable tool to study the role of salivary molecules in parasite-host/vector interactions.

Guanylin and Functional Coupling Proteins in the Human Salivary Glands and Gland Tumors: Expression, Cellular Localization, and Target Membrane Domains

Cystic fibrosis transmembrane conductance regulator (CFTR)-mediated secretion of an electrolyte-rich fluid is a major but incompletely understood function of the salivary glands. We provide molecular evidence that guanylin, a bioactive intestinal peptide involved in the CFTR-regulated secretion of electrolyte/water in the gut epithelium, is highly expressed in the human parotid and submandibular glands and in respective clinically most relevant tumors. Moreover, in the same organs we identified expression of the major components of the guanylin signaling pathway, ie, guanylin-receptor guanylate cyclase-C, cGKII, and CFTR, as well as of the epithelial Cl(-)/HCO(3)(-) anion exchanger type 2 (AE2). At the cellular level, guanylin is localized to epithelial cells of the ductal system that, based on its presence in the saliva, is obviously released into the salivary gland ducts. The guanylin-receptor guanylate cyclase-C, cGKII, CFTR, and AE2 are all confined exclusively to the apical membrane of the same duct cells. These findings implicate guanylin as intrinsic regulator of electrolyte secretion in the salivary glands. We assume that duct epithelial cells synthesize and release guanylin into the saliva to regulate electrolyte secretion in the ductal system by an intraductal luminocrine signaling pathway. Moreover, the high expression of guanylin in pleomorphic adenoma and Warthin tumors (cystadenolymphoma), the most common neoplasms of salivary glands, predicts guanylin as a significant marker in tumor pathology.

The effect of external fractionated irradiation on the distribution pattern of extracellular matrix proteins in submandibular salivary glands of the rat

Introduction: The aim of this study was to analyse the distribution pattern of extracellular matrix proteins in the irradiated and non-irradiated rat submandibular salivary gland in order to provide a more detailed profile of the radiation injury following radiotherapy of the head and neck. Material and Methods: External X-ray exposure, restricted to the left skull base and neck region, was performed in 60 female Wistar rats, fractionated to daily applications of 2 Gy, up to total dosages of 20, 40 or 60 Gy. Both submandibular glands were excised after supravital anaesthesia 6 months or 1 year after completion of the irradiation. Spatial and temporal patterns of extracelluar matrix proteins were investigated histologically and immunohistochemically. Results: The polyclonal anti-human antisera used, identified the same antigens in rat tissue as in human tissues. The alterations in staining patterns and staining intensities between irradiated and non-irradiated salivary glands showed statistically significant differences. Different structures in irradiated glands reacted with different intensities, e.g. nerve tissue and the basement membranes of excretory ducts were intensely laminin-positive, fibronectin was predominantly found around the excretory ducts with transition to the interstitial tissues. Conclusion: Irradiation leads to statistically significant differences in the amount and composition of the extracellular matrix in salivary glands. The amount of extracellular matrix proteins in irradiated glands is dose-dependent. The higher the dosage the more extracellular matrix can be expected. Consecutively, total dosage is associated with greater loss of acini. Scatter effects of irradiation have also to be recognized. Immunohistochemical studies on salivary glands have to consider the pretreatment status, in particular those studies that investigate degenerative changes. Copyright 2002 European Association for Cranio-Maxillofacial Surgery. Published by Elsevier Science Ltd. All rights reserved.

The major acid soluble proteins of adult female Anopheles darlingi salivary glands include a member of the D7-related family of proteins

The salivary gland proteins of adult female Anopheles darlingi were fractionated by reverse-phase HPLC and the five major peaks were submitted for amino-terminal sequencing using automated Edman degradation. The amino acid sequence of one of the purified salivary gland proteins showed similarity with the D7r3 protein of An. gambiae. Cloning and sequencing of two cDNAs allowed the prediction of the complete sequence of the An. darlingi D7 protein. The D7r3 protein is present specifically in adult female salivary glands of An. darlingi and despite being one of the major salivary gland proteins its function is not known. Predictions of secondary and tertiary structures revealed the similarity of the An. darlingi D7 protein to insect odorant binding proteins. This suggests that D7 proteins may act as carriers of hydrophobic molecules in mosquito saliva.

Expression of D7 and D7-related proteins in the salivary glands of the human malaria mosquito Anopheles stephensi.

Full-length cDNA clones encoding D7 (AnsD7) and D7-related (AnsD7r1) secreted salivary gland proteins were isolated from Anopheles stephensi. Corresponding proteins were separated by SDS-PAGE and analysed by N-terminal sequencing, which also identified a second D7-related protein (AnsD7r2). AnsD7 encodes a protein of 37 kDa, AnsD7r1 of 18 kDa, and AnsD7r2 of 16 kDa. Polyclonal antibodies against recombinant AnsD7 showed immunological cross-reactivity with the D7-related proteins, and alignment demonstrated sequence similarity between the C-terminal region of AnsD7 and the D7-related proteins. AnsD7, AnsD7r1 and AnsD7r2 were major female-specific salivary gland proteins, and Western blotting, immunohistochemistry and immunogold labelling demonstrated expression was predominantly in the secretory cavities of the distal-lateral and median lobes. Expression and localization of D7 and D7-related proteins was similar in Plasmodium berghei-infected and uninfected mosquitoes.

Identification of major soluble salivary gland proteins in teneral Glossina morsitans morsitans

Salivary glands of tsetse flies (Diptera: Glossinidiae) contain molecules that are involved in preventing blood clotting during feeding as well as molecules thought to be intimately associated with trypanosome development and maturation. Here we present a protein microchemical analysis of the major soluble proteins of the salivary glands of Glossina morsitans morsitans, an important vector of African trypanosomes. Differential solubilization of salivary proteins was followed by reverse-phase, high-performance liquid chromatography (HPLC) and analysis of fractions by 1-D gel electrophoresis to reveal four major proteins. Each protein was subjected to amino acid microanalysis and N-terminal microsequencing. A protein chemical approach using high-resolution 2-D gel electrophoresis and mass spectrometry was also used to identify the salivary proteins. Matrix-assisted, laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry and quadrupole time-of-flight (Q-TOF) tandem mass spectrometry methods were used for peptide mass mapping and sequencing, respectively. Sequence information and peptide mass maps queried against the NCBI non-redundant database confirmed the identity of the first protein as tsetse salivary gland growth factor-1 (TSGF-1). Two proteins with no known function were identified as tsetse salivary gland protein 1 (Tsal 1) and tsetse salivary gland protein 2 (Tsal 2). The fourth protein was identified as Tsetse antigen-5 (TAg-5), which is a member of a large family of anti-haemostatic proteins. The results show that these four proteins are the most abundant soluble gene products present in salivary glands of teneral G. m. morsitans. We discuss the possible functions of these major proteins in cyclical transmission of African trypanosomes.

Molecular cloning and partial characterization of a trypsin-like protein in salivary glands of Lygus hesperus (Hemiptera: Miridae)

Trypsin-like enzymes from the salivary gland complex (SGC) of Lygus hesperus Knight were partially purified by preparative isoelectric focusing (IEF). Enzyme active against Nα-benzoyl- l-arginine- p-nitroanilide (BA pNA) focused at approximately pH 10 during IEF. This alkaline fraction gave a single activity band when analyzed with casein zymograms. The serine proteinase inhibitors, phenylmethylsulfonyl fluoride (PMSF) and lima bean trypsin inhibitor, completely inhibited or suppressed the caseinolytic activity in the crude salivary gland extract as well as the IEF-purified sample. Chicken egg white trypsin inhibitor also inhibited the IEF-purified sample but was not effective against a major caseinolytic band in the crude salivary gland extract. These data indicated the presence of serine proteinases in the SGC of L. hesperus. Cloning and sequencing of a trypsin-like precursor cDNA provided additional direct evidence for serine proteinases in L. hesperus. The encoded trypsin-like protein included amino acid sequence motifs, which are conserved with five homologous serine proteinases from other insects. Typical features of the putative trypsin-like protein from L. hesperus included residues in the serine proteinase active site (His 89, Asp 139, Ser 229), conserved cysteine residues for disulfide bridges, residues (Asp 223, Gly 252, Gly 262) that determine trypsin specificity, and both zymogen signal and activation peptides.

Neural control of salivary S-1gA secretion

Salivary-immunoglobulin A (S-IgA) secretion into the saliva of humans is rapidly increased (within 15 s) by autonomic nerve-mediated reflex stimuli through increased glandular epithelial cell transcytosis of IgA by polymeric immunoglobulin receptor (pIgR). Investigations in rat salivary glands have revealed that such autonomic regulation is mediated through both sympathetic and parasympathetic nerves and that a number of epithelial cell autonomic receptors are involved, although cholinergic stimuli appear to have a lesser effect than adrenergic and peptidergic stimuli. The autonomic regulation of S-IgA secretion is different from the major stored secretory proteins of salivary glands, so it is concluded from in vivo studies that stimulated secretion is on or off and does not show dose dependency or additive effects with combinations of agonists. Autonomic nerves have longer-term effects on S-IgA secretion through effects on pIgR-mediated transcytosis as demonstrated by denervation experiments. Stress or extensive, intense physical training are linked with increased susceptibility to upper respiratory tract infections and decreased S-IgA secretion plays a significant role. S-IgA secretion is under the influence of the autonomic nervous system but further studies are required to determine whether altered autonomic activity can change susceptibility to mucosal infection.

Salp25D, an Ixodes scapularis antioxidant, is 1 of 14 immunodominant antigens in engorged tick salivary glands.

Rabbits or guinea pigs infested with Ixodes scapularis acquire resistance to tick bites, a phenomenon, known as tick immunity, that is partially mediated by antibody. To determine the salivary gland antigens that elicit antibodies in the host, an I. scapularis salivary gland cDNA expression library was probed with serum from tick-immune rabbits. Sera from sensitized rabbits strongly recognized 47 of 100,000 library clones in an antibody-screening assay. These 47 clones encoded 14 different I. scapularis genes, including a glutathione peroxidase homologue. Expression of these 14 genes in engorged tick salivary glands was confirmed by reverse-transcription polymerase chain reaction. The I. scapularis glutathione peroxidase homologue, named salp25D, was expressed in both unfed and fed nymphal salivary glands. Recombinant Salp25D was able to catalyze the reduction of hydrogen peroxide in the presence of reduced glutathione and glutathione reductase. These results categorize the prominent salivary gland proteins in I. scapularis and demonstrate the presence of a potent antioxidant in tick saliva.

Toward a defined anti-Leishmania vaccine targeting vector antigens: characterization of a protective salivary protein.

Leishmania parasites are transmitted to their vertebrate hosts by infected phlebotomine sand fly bites. Sand fly saliva is known to enhance Leishmania infection, while immunity to the saliva protects against infection as determined by coinoculation of parasites with vector salivary gland homogenates (SGHs) or by infected sand fly bites (Kamhawi, S., Y. Belkaid, G. Modi, E. Rowton, and D. Sacks. 2000. Science. 290:1351-1354). We have now characterized nine salivary proteins of Phlebotomus papatasi, the vector of Leishmania major. One of these salivary proteins, extracted from SDS gels and having an apparent mol wt of 15 kD, was able to protect vaccinated mice challenged with parasites plus SGH. A DNA vaccine containing the cDNA for the predominant 15-kD protein (named SP15) provided this same protection. Protection lasted at least 3 mo after immunization. The vaccine produced both intense humoral and delayed-type hypersensitivity (DTH) reactions. B cell-deficient mice immunized with the SP15 plasmid vaccine successfully controlled Leishmania infection when injected with Leishmania plus SGH. These results indicate that DTH response against saliva provides most or all of the protective effects of this vaccine and that salivary gland proteins or their cDNAs are viable vaccine targets against leishmaniasis.

Identification of putative proteins involved in granule biogenesis of tick salivary glands.

Ticks secrete bioactive components during feeding that assist them in gaining a blood meal. Compounds secreted are stored in granules until a stimulus induces secretion during feeding. Biogenesis of tick secretory granules has not been investigated before. An adequate understanding of granule biogenesis could advance our understanding of tick salivary gland biology and could aid in the rational design of tick control methods. Putative tick salivary gland proteins 1-4 (TSGP1-4) involved in granule biogenesis were identified in this study based on their abundance in salivary gland extracts and granule preparations and their ability to aggregate under conditions of slight acidity and high calcium concentration. TSGP2 and TSGP3 have been identified as previously described toxic and nontoxic homologues, respectively, while toxicity was also associated with TSGP4.

Abnormal Distribution of Aquaporin-5 Water Channel Protein in Salivary Glands from Sjögren's Syndrome Patients

Patients with Sjögren's syndrome (SS) suffer from deficient secretion of saliva due to an autoimmune destruction of salivary glands, however, glandular dysfunction also occurs without destruction. Based upon its abnormal distribution in SS salivary glands, a potential role for the water channel protein aquaporin-5 (AQP5) is proposed in the pathogenesis of SS. The immunohistochemical distribution of AQP5 was compared in minor salivary gland biopsies obtained from women after informed consent: primary SS (53.2 ± 14 years old, n = 10), healthy volunteers (46.2 ± 17 years old, n = 10), patients with sarcoidosis (37 and 48 years old), and patients with non-specific sialoadenitis (54 and 61 years old). Biopsies from normal subjects revealed AQP5 primarily at the apical membrane of the salivary gland acinus. In contrast, biopsies from SS patients revealed AQP5 primarily at the basal membranes of the acinus. The AQP5 distribution in biopsies from patients with other dry mouth disorders, such as non-specific sialoadenitis or sarcoidosis, was similar to biopsies from control subjects. Computer-assisted microscopy was performed to quantitatively evaluate AQP5 distribution in the immunoreactive acini of both SS and control subjects. Biopsies from SS patients had higher labeling indices (percentage of acinus area immunoreactive for AQP5) at the basal membrane when compared with biopsies from control subjects. In contrast, biopsies of SS patients exhibited lower labeling indices at the apical membrane when compared with biopsies from control subjects. To verify the specificity of the AQP5 antibody, Western blot analysis was performed on membranes from Xenopus oocytes injected with AQP5 cRNA or on membranes from minor salivary glands of control subjects and SS patients. In each case, the immunoblots had a 27 kd band, corresponding to the expected molecular weight of AQP5. Abnormal distribution of AQP5 in salivary gland acini is likely to contribute to the deficiency of fluid secretion, which is a defining feature of Sjögren's syndrome.

Cattle Natural immunity against the cattle tick Boophilus annulatus (Acari: Ixodidae): detection of antibodies against salivary gland and gut proteins using ELISA

Blood samples were taken from 50 cattle (5 Bos indicus, 5 crossbreeds between B. indicus and Bos taurus, and 40 B. taurus, Frizian strain). There was no Boophilus (B.) annulatus Say infestation on 5 B. indicus; moderate infestation on the crossbreeds and heavy infestation on B. taurus. Ticks collected from B. taurus were dissected to obtain salivary glands (S) and guts (G). The tick organs were processed for separation of proteins with 7% polyacrylamide gel electrophoresis (PAGE). Seven gut protein bands of molecular weights 2000, 1500, 500, 205, 150, 66, and 12 KDa were designated G1, G2, G3, G4, G5, G6, G7 and four salivary gland protein bands of molecular weights 205, 190, 150 and 97 KDa were designated S1, S2, S3, S4. All were used as tick antigens for the detection of antibodies by an enzyme-linked immunosorbent assay (ELISA). It was found that all 5 B. indicus and 5 crossbreeds had antibodies to all salivary gland proteins employed in the ELISA test. All B. taurus had antibodies to G1 and to the other tick proteins in variable percentage. The results indicated that B. indicus and the crossbreeds had immunity to B. annulatus antigens correlated with none or moderate tick infestation, respectively. The lack of antibodies to some tick antigens in Bos taurus correlated with high tick infestation.

Boophilus annulatus (Acari: Ixodidae): cattle-acquired humoral and cell-mediated immunity against tick gut and salivary gland antigens

Assays of antibodies and cell-mediated immunity (CMI) against specific antigens in Boophilus (B.) annulatus Say gut and salivary glands were performed using Bos indicus cattle infested for prolonged periods as a model for naturally acquired immunity to ticks. It was shown that cattle sera contained several antibodies that were reactive with gut proteins (45,66,116,150, and 274 KDa Mol. Wt.) and with salivary gland proteins (66,97,150 and 205 KDa Mol. Wt.) by an enzyme-linked immunosorbent assay (ELISA) and dot immunoblot assays. CMI positive responses to both gut proteins (2000 and 150 KDa Mol. Wt.) and salivary gland protein (150 KDa Mol. Wt) were observed by a macrophage migration inhibition (MMI) test. The potential usefulness of B. annulatus antigenic proteins for vaccination of local cattle breeds is the subject of an ongoing study.

Anopheles gambiae salivary gland proteins as putative targets for blocking transmission of malaria parasites.

Anopheles gambiae is the primary vector of human malaria in sub-Saharan Africa. Invasion of Anopheles salivary glands by Plasmodium sporozoites is a necessary step in the transmission of malaria and is likely to be mediated by specific receptor-ligand interactions. We are interested in identifying putative an A. gambiae salivary gland receptor or receptors for sporozoite invasion as a possible target for blocking malaria transmission. By using monoclonal antibodies against female-specific A. gambiae salivary gland proteins, two molecules, one of 29 kDa and one of 100 kDa, were identified and characterized with respect to the age and blood-feeding process of mosquitoes. In an in vivo bioassay, the monoclonal antibody against the 100-kDa protein inhibited Plasmodium yoelii sporozoite invasion of salivary glands >/=75%. These results show that A. gambiae salivary gland proteins are accessible to monoclonal antibodies that inhibit sporozoite invasion of the salivary glands and suggest alternate targets for blocking the transmission of malaria by this most competent of malaria vectors.

Prostaglandin E 2-stimulated secretion of protein in the salivary glands of the lone star tick via a phosphoinositide signaling pathway

Previous studies identified a prostaglandin E 2 (PGE 2) receptor in the salivary glands of partially fed female lone star ticks, Amblyomma americanum (L.). In the present studies, protein secretion from dispersed salivary gland acini was shown to be specific for PGE 2, as compared with PGF 2α or the thromboxane analog U-46619, in accordance with their respective binding affinities for the PGE 2 receptor. Furthermore, the selective PGE 2 EP1 receptor agonist, 17-phenyl trinor PGE 2, was as effective as PGE 2 in stimulating secretion of anticoagulant protein. Calcium ionophore A-23187 (1 to 100 μM) stimulated secretion of anticoagulant protein in a dose-dependent manner but the voltage-gated Ca 2+-channel blocker verapamil (1 to 1000 μM) and the receptor-mediated Ca 2+-entry antagonist, SK&F 96365 (1 and 10 μM), and 5 mM ethylene glycol bis(β-aminoethyl ether)-N,N N′, N′-tetraacetic acid (EGTA) had no appreciable effect on inhibiting PGE 2-stimulated secretion of anticoagulant protein. PGE 2 (0.1 μM) and the non-hydrolyzable analog of guanosine triphosphate (GTP), GTPγS (10 μM), directly activated phospholipase C (PLC) in a membrane-enriched fraction of the salivary glands after PLC was first incubated with the PGE 2 EP1 receptor antagonist AH-6809, which presumably antagonized endogenous PGE 2 (0.3 μM) in the broken-cell-membrane-enriched fraction. TMB-8, an antagonist of intracellular inositol trisphosphate (IP 3) receptors, inhibited PGE 2-stimulated secretion. The results support the hypothesis that PGE 2 stimulates secretion of tick salivary gland protein via a phosphoinositide signaling pathway and mobilization of intracellular Ca 2+.

Salivary proteins and glycoproteins in phlebotomine sandflies of various species, sex and age.

Salivary gland proteins were studied in sandflies (Diptera: Psychodidae: Phlebotominae) by electrophoretic techniques. In Phlebotomus duboscqi Neveu-Lemaire the protein concentration was about 30 times higher in females than in males. SDS PAGE revealed eight major bands of 29-62 kDa in salivary gland extracts (SGE) from females, whereas only one band of 57kDa was detected in males. The number of protein components in SGE gradually increased with the age of females. In P. papatasi (Scopoli) the typical electrophoretic pattern was reached in 3-5 days after imago emergence, depending on the temperature at which females were maintained. All major protein components of the female SGE were present in the content of glands. Female SGE were compared in seven colonies of five Phlebotomus and Lutzomyia species; electrophoretic profiles distinguished between species and even between colonies of different geographical origin. In general, the highest variability of major protein components was observed in the 38-48kDa region. Four colonies of the subgenus Phlebotomus (P. duboscqi and P. papatasi) possessed common mobility polypeptides, the highest similarity was found between two colonies of P. papatasi. Other species tested significantly differed, specific prominent bands of 33, 35 and 38kDa were found in P. halepensis Theodor, P. perniciosus Newstead and Lutzomyia longipalpis (Lutz & Neiva), respectively. Glycoproteins in SGE of Lu. longipalpis and P. duboscqi females were identified and analysed using blotting with five lectin conjugates. Specific reaction of lectins ConA and WGA revealed the complex type of N-glycans in the 48 and 53-54kDa glycoproteins present in both species. Similar glycosylation was detected in species-specific bands of the 57-60 and 65-67 kDa in P. duboscqi and Lu. longipalpis, respectively. The high mannose type of glycosylation was found in the 20 and 39 kDa polypeptides of Lu. longipalpis and the 40-42 kDa polypeptides of P. duboscqi. Innate lectin activity specific for aminosugars was detected in SGE of P. duboscqi females using haemagglutination tests with rabbit erythrocytes.

Chaperones in the Parotid Gland: Localization of Heat Shock Proteins in Human Adult Salivary Glands

Heat shock proteins (HSPs) are expressed or increased in response to various biological stresses. Moreover, these ‘stress proteins’ seem to be expressed by some cells living in physiological conditions. From then on, they could play an important physiological role in normal cell functioning. The best-known physiological role of these HSP proteins is to act as ‘molecular chaperones’. In this context, we have investigated the immunohistochemical expression of HSP27, HSP70, HSP90 and HSP110 in 10 human adult salivary glands. To highlight the presence of RNAm encoding HSP70, an in situ hybridization was performed. In our material, HSP27 was strongly expressed in the cytoplasm of striated duct cells and in some myoepithelial cells. The same localization was less stained for HSP70 and HSP90. The immunocytochemical reaction was weak or negative for HSP110 in striated ducts. HSPs were not expressed in acinic cells. In situ hybridization gave a positive signal in striated ducts with a probe encoding HSP70. Epithelial cells of the striated ducts and myoepithelial cells expressed HSP27, HSP70 and HSP90. These HSPs probably act in part as molecular chaperones for protein synthesis, transport and for several interactions between HSPs and different proteins.

Regulation and Function of Scr, exd, and hth in the Drosophila Salivary Gland

Salivary gland formation in the Drosophila embryo is dependent on the homeotic gene Sex combs reduced (Scr). When Scr function is missing, salivary glands do not form, and when SCR is expressed everywhere in the embryo, salivary glands form in new places. Scr is normally expressed in all the cells that form the salivary gland. However, as the salivary gland invaginates, Scr mRNA and protein disappear. Homeotic genes, such as Scr, specify tissue identity by regulating the expression of downstream target genes. For many homeotic proteins, target gene specificity is achieved by cooperatively binding DNA with cofactors. Therefore, it is likely that SCR also requires a cofactor(s) to specifically bind to DNA and regulate salivary gland target gene expression. Here, we show that two homeodomain-containing proteins encoded by the extradenticle (exd) and homothorax (hth) genes are also required for salivary gland formation. exd and hth function at two levels: (1) exd and hth are required to maintain the expression of Scr in the salivary gland primordia prior to invagination and (2) exd and hth are required in parallel with Scr to regulate the expression of downstream salivary gland genes. We also show that Scr regulates the nuclear localization of EXD in the salivary gland primordia through repression of homothorax (hth) expression, linking the regulation of Scr activity to the disappearance of Scr expression in invaginating salivary glands.

Salivary gland proteins of the mosquito Culex quinquefasciatus.

Several properties of the salivary glands of Culex quinquefasciatus mosquitoes were analysed. The amount of protein in female salivary glands increased from 0.26 microg on day one after emergence to about 1.4 microg on day seven. The major polypeptides found in the female salivary glands had molecular weights of 35.7, 28.3, and 20.5 kDa. Antibodies produced by mice immunized by bites of Culex quinquefasciatus female mosquitoes reacted with the 35.7 and 28.3 kDa polypeptides, showing that these molecules were secreted by mosquitoes during blood feeding. The salivary glands of C. Quinquefasciatus females displayed the same morphological and biochemical organization as that of Aedes aegypti mosquitoes, accumulating apyrase in the distal portions and alpha-glucosidase in the proximal portions of the gland. Arch.