CELL-MEMBRANE RECEPTORS AND REGULATION OF CELL-FUNCTION IN TICKS AND BLOODSUCKING INSECTS

Cell membrane receptors and regulation of cell function in ticks and b lood-sucking insects. International Journal for Parasitology 24: 33-52 . Immunoglobulins cross the midgut epithelium and enter the haemolymph of many blood-feeding arthropods without losing their immunological p roperties. Antigens essential to the survival of the bloodsucking arth ropods which may be affected by the small amounts of specific antibody that cross the gut epithelium include membrane receptors or other fac tors which regulate cell function. Membrane receptors implicated in tr ansmembrane signalling in response to specific neural and endocrine fa ctors fall into three major classes: (1) gated ion channels, (2) agoni st-stimulated tyrosine kinases and (3) receptors that interact with GT P-binding (G) proteins. Examples of all three types have been found in insects and ticks. A dopamine receptor interacts with a G-protein ess ential for controlling fluid secretion by the salivary glands of ixodi d ticks. Another receptor in the ixodid tick salivary gland binds a ne uropeptide from the tick synganglion and stimulates turnover of plasma membrane phosphoinositides, but its mechanisms of transmembrane signa lling and function remain elusive. Another large class of membrane rec eptors are those concerned with endocytosis. Examples of receptor-medi ated endocytosis include incorporation of vitellogenin by developing o ocytes in mosquitoes and ticks and uptake of lysed blood-meal componen ts by digest cells of the tick gut. Many cell membrane receptors and p ossibly hormones could serve as targets for vaccines in blood-feeding insects and ticks. The major challenge is to identify and characterize essential internal receptors and cellular components that are accessi ble to and affected by specific antibodies that are introduced into th e body of blood-feeding arthropods.