Braz. J. morphol. Sci. (2005) 22(4), 211-214 ISSN- 0102-9010 Correspondence to: Dr. Tales Alexandre Aversi-Ferreira Departamento de Morfologia, Instituto de Ciências Biológicas (ICB IV), Universidade Federal de Goiás (UFG), Campus Samambaia, CEP 74001-190, Goiânia, GO, Brasil. Tel: (55) (62) 3521-1232, Fax: (55) (62) 3521-1178, E-mail: aversiferreira@yahoo.com.br IMMUNOELECTRONIC LOCALIZATION OF MYOSIN-Va IN RAT CEREBELLUM Tales Alexandre Aversi-Ferreira 1 , Nilson Penha-Silva 2 , James Ferreira dos Santos 2 , Antônio Wilson de Almeida 3 , Foued Salmen Espíndola 2 1 Department of Morphology, Institute of Biological Sciences, Federal University of Goiás, Goiânia, GO, Brazil, 2 Institute of Genetics and Biochemistry, Federal University of Uberlândia, Uberlândia, MG, Brazil, 3 University of Patos de Minas, Patos de Minas, MG, Brazil. ABSTRACT Myosin V is an unconventional type of actin-binding myosin that participates in cytoplasmic organelle transport. Although this unconventional myosin has been extensively studied, its subcellular localization in the mammalian cerebellum has not been determined. In this work, we used an antibody against the tail domain of the myosin-Va heavy chain and a secondary antibody labeled with protein A-gold (15 nm) to study the subcellular distribution of this protein. Myosin-Va was found in the cytoplasm, where it was associated with a filament (probably actin). This protein was also detected in the plasma membrane of axons and dendrites in the molecular layer in rat cerebellum. Key words: Cerebellum, electronic microscopy, myosin-Va, Purkinje cells INTRODUCTION Myosin-Va is an important member of a group of proteins collectively known as myosin-V. These proteins are involved in various cellular functions, including intracellular transport, signal transduction and the mechanoregulation of channels [28]. Myosin- V has been detected in cultured vertebrate [29] and invertebrate [26] neural cells, in proteins extracted from vertebrate brains [3,21], in the neural enteric system of rats [6], in guinea pig cochlea [4], and in the centrosome of the rat hippocampus [8]. Myosin- V has also been found in the dendritic and axonal terminations (growth cones) of chicken neurons [9,10,23,29], where it is responsible for the fusion of synaptic vesicles with the plasma membrane [21]. Other actin-binding proteins have also been found in neuronal cytoplasm of the adult rat forebrain [15,14,29]. Myosin-V belongs to a superfamily of myosins found in lower and higher eukaryotes [29] and was originally identified as an ATPase-dependent, calmodulin-binding protein [7,29]. Structurally, myosin-V contains two heads connected to a long chain with 12 light chains. As a motor protein, myosin-V associates with actin [17] and is involved in the movement of cellular organelles [4,24] and in the segregation and generation of subcellular compartments [29]. Myosin-V is also associated with the membranes of melanosomes, synaptic vesicles and the smooth endoplasmatic reticulum [19,29] in the growing cones of neurons [2,29] and in synaptosomes of the rat cerebral cortex [29]. In neurons, the motor activity that results from the association of myosin-V with actin contributes to the formation of dendritic spines and to the formation of new connections [10]. A lack of myosin-V results in neural and pigmentation deficiencies in mice and humans [3], with these deficiencies being characteristic of the rare Griscelli syndrome in humans [13]. The sublocalization of unconventional myosins, mainly myosin-V, may provide morphological evidence that would be helpful in understanding the movements or formation of dendritic spines in adult mammalian brains. In this work, we examined the sublocalization of myosin-V in adult rat cerebellum. MATERIAL AND METHODS The procedures involving animals were done within the guidelines of the Brazilian College for Animal Experimentation (COBEA) and were approved by the institutional ethics committee of the Federal University of Uberlândia. Four male Wistar rats (270 ± 32 g) that had been housed at 22 + 0.4°C, on a 12 h light/dark cycle, with free access to water and food were anesthetized intramuscularly with a mixture of xylazine (40 mg/kg)