Calmodulin expression during Giardia intestinalis differentiation and identification of calmodulin-binding proteins during the trophozoite stage

Abstract

Calmodulin (CaM) is the primary sensor for calcium in the cell. It modulates various functions by activating CaM-binding proteins (CaMBPs). This study examined the calcium/CaM-dependent system in the ancient eukaryote Giardia intestinalis. A specific antibody against the parasite's CaM was developed; this protein's expression and location during different stages of the parasite's life cycle were analyzed. The results showed that it is a housekeeping protein which is possibly involved in the parasite's motility. No CaMBP has been identified in G. intestinalis to date. Pull-down assays were used for isolating proteins which specifically bind to CaM in a calcium-dependent way. Three of them were identified through mass spectrometry; they were GASP180, α-tubulin, and pyruvate phosphate dikinase (PPDK).The first two are cytoskeleton proteins, and the last one is an essential enzyme for glycolysis. The presence of binding sites was analyzed through bioinformatics in each protein sequence. This is the first report of a CaMBP in this organism; it is considered to be a very interesting differentiation model, indicating that CaM is involved at least in two vital processes: G. intestinalis motility and energetic metabolism.

Characterization and identification of calmodulin and calmodulin binding proteins in hemocyte of the black tiger shrimp (Penaeus monodon)

“…In 2011, Alvarado and Wasserman successfully isolated GASP180, α-tubulin and pyruvate phosphate dikinase from tropozoite stage of Giardia intestinalis that were calcium-dependent proteins. The first two proteins were classified in cytoskeleton proteins and the other was an essential enzyme in glycolysis pathway, suggesting the function of CaM in motility and energetic metabolism (Alvarado and Wasserman, 2012). However, the function of CaM, especially in signal transduction and immune system, is still unclear.…”

Membrane associated proteins of two Trichomonas gallinae clones vary with the virulence

“…These proteins can be found in organelle membranes and play a role in the activation of phosphorylase kinases or phosphatases, necessary for cytoskeletal re-organization. Calmodulin is involved in the movement of Giardia intestinalis [38] and a calmodulin-like protein has been identified in E . histolytica playing a role in the phagocytosis of erythrocytes and cytoskeleton dynamics [39].…”

Molecular and Biochemical Characterization of Calmodulin from<em> Echinococcus granulosus</em>

“…This phenomenon further implies that calmodulin is related to exocytic activity in protoscoleces. By studying other target proteins of calmodulin, such as myosin and GASP180, some important physiological activities which require calmodulin have been discovered in parasites [19,29]. In a previous study, calmodulin depletion resulted in total and catastrophic failure in paraflagellar rod assembly of Trypanosoma brucei [21].…”