Additional remarks phenotype | Mutant/mutation
The mutant expresses a C-terminal mCherry tagged version of IMC1c in which the three carboxy-terminal cysteines have been substituted (wild type IMC1c: ... AKPVGCCTGTCR; mutant IMC1c: ... AKPVGLETGTWR)
Protein (function)
The three motile and invasive stages (zoites) of Plasmodium species (i.e. ookinetes, sporozoites and merozoites), as well as zoites of other apicomplexan parasites, possess a similar cortical structure termed the pellicle. The pellicle is essentially made up of the plasma membrane and an underlying double membrane structure termed the inner membrane complex (IMC). Closely associated with the IMC on its cytoplasmic side is a network of intermediate filaments termed the subpellicular network (SPN), which supports the pellicular membranes and provides mechanical strength to the cell. Several members of an Apicomplexa-specific family of proteins termed IMC1 proteins have been identified as components of the SPN. Structurally related proteins from ciliates and dinoflagellate algae have since been added to this protein family renamed ‘alveolins’, which now defines the Alveolata infrakingdom. In the genus Plasmodium, the number of members of the alveolin family has risen to 12, which are encoded by conserved and syntenic genes. The alveolin family members display differential expression between the three zoite stages of the parasite, with the largest repertoires present in the ookinete and sporozoite according to proteomic studies. It has been shown in the rodent malaria species Plasmodium berghei that the disruption of individual alveolin family members expressed in sporozoites (PbIMC1a), in ookinetes (PbIMC1b) or in both these zoites (PbIMC1h) results in morphological abnormalities that are accompanied by reduced tensile strength of the zoite stages in which they are expressed. Besides roles in morphogenesis and mechanical strength, the Plasmodium alveolins are also involved in gliding motility in both ookinetes and sporozoites, most likely through interactions with components of the glideosome that are situated within the pellicular cytoplasm.
PbIMC1c is composed of 278 amino acids encoded by a single exon. PbIMC1c and its orthologous. proteins share a highly conserved amino-terminal domain related to the IMCp domain superfamily (Pfam12314) that defines the IMC1 proteins/alveolins.
PbIMC1c and its Plasmodium orthologues have a single conserved cysteine motif at their carboxy-terminus that is predicted to act as a palmitoylation site. In P. falciparum, the protein was detected in the palmitoylated proteome of asexual blood stages indicating that it is indeed palmitoylated. PbIMC1c is expressed in all three zoites where it displays a cortical localisation consistent with that of the SPN, and is essential for asexual blood stage parasite development (see RMgm-1120 for unsuccessful attempts to disrupt Pbimc1c)
Phenotype
See RMgm-1122 for a 'wild type' mutant expression mCherry-tagged IMC1c. This mutant showed mCherry expression in merozoites, ookinetes and sporozoites.
IMC1c/mCherry-Mutant 1 showed normal asexual blood stage growth, production of ookinetes, oocysts and infective sporozoites demonstrating that the carboxy-terminal cysteine motif of PbIMC1c is dispensable for parasite development in the mouse and mosquito.
Evidence is presented that mutant ookinetes possess reduced tensile strength compared to wild type ookinetes as determined in hypo-osmotic exposure experiments
Additional information
Evidence is presented that IMC1c is palmitoylated on its carboxy-terminal cysteine motif.
From the summary: 'These findings support the hypothesis that alveolin (IMC1c) palmitoylation enhances cytoskeletal function by strengthening the connection between the subpellicular network (SPN) and the adjoining inner membrane complex via lipid anchoring'
Other mutants
See IMC1c |