Anti-TBBC antibodies detected a TBBC-like component in the centrosome of mammalian cells such as HeLa cells and mouse spermatozoa. MATERIALS AND METHODS

Trypanosoma brucei is a protozoan flagellate responsible for several severe diseases in various mammals, including the nagana disease in cattle and human sleeping sickness. This parasite is transmitted by the tsetse fly, where it develops in the midgut as the so called procyclic form which proliferates rapidly. Once the trypanosomes have reached the fly salivary glands they transform into quiescent metacyclic forms which are preadapted to the bloodstream environment. After injection into the mammalian host upon biting by infected flies, trypanosomes proliferate as bloodstream slender forms until they stop dividing and differentiate into stumpy forms which are preadapted to the fly (Vickerman, 1985; Vickerman et al., 1988). The cytoskeleton of T. brucei is composed essentially of a microtubule cage which is responsible for maintaining the shape and the form of the cell, and a flagellum used for motility and attachment to the membranes of host cells (Hemphill et al., 1991; Kohl and Gull, 1998). The flagellum is composed of the classical axoneme together with a structure identified in Euglenoids, Dinoflagellates and Kinetoplastids termed the paraflagellar rod (Schlaeppi et al., 1989; Deflorin et al., 1994; Bastin et al., 1996), and the basal body. The basal body is a centriole-like structure located at the base of the flagellum. The role of centrioles and the pericentriolar material as microtubule organizing centers (MTOC) has been progressively clarified (Marshall and Rosenbaum, 1999) but the MTOC activity of the basal body is still poorly understood. Like the centrioles, the basal body is complexed with accessory structures. In T. brucei, the basal body seems to play at least three different roles. During cell division this structure directs the assembly of the new axoneme and is involved in mitochondrial DNA (kinetoplast) segregation (Robinson and Gull, 1991). In addition, it is believed to play a role in the organisation of four particular microtubules from the corset which unlike other microtubules arise from the basal body region and probably show inverted polarity (Khol and Gull, 1998). These microtubules are a part of the flagellar attachment zone (FAZ) and are associated with the smooth endoplasmic reticulum (Vickerman, 1969; Sherwin and Gull, 1989). Here we describe the serendipitous discovery of a new basal body component. In an attempt to identify the gene for a T. brucei immunosuppressive factor, we cloned a gene encoding a 212 kDa cytoskeletal protein which is expressed in the three major developmental stages of the parasite. Immunofluorescence microscopy showed that this protein is mainly located in the basal body and also in the posterior end of the cell, the flagellum and the nucleus. Anti-TBBC antibodies detected a TBBC-like component in the centrosome of mammalian cells such as HeLa cells and mouse spermatozoa.