Expansion microscopy provides new insights into the cytoskeleton of malaria parasites including the conservation of a conoid

Malaria is caused by unicellular Plasmodium parasites. Plasmodium relies on diverse microtubule cytoskeletal structures for its reproduction, multiplication, and dissemination. Due to the small size of this parasite, its cytoskeleton has been primarily observable by electron microscopy (EM). Here, we demonstrate that the nanoscale cytoskeleton organisation is within reach using ultrastructure expansion microscopy (U-ExM). In developing microgametocytes, U-ExM allows monitoring the dynamic assembly of axonemes and concomitant tubulin polyglutamylation in whole cells. In the invasive merozoite and ookinete forms, U-ExM unveils the diversity across Plasmodium stages and species of the subpellicular microtubule arrays that confer cell rigidity. In ookinetes, we additionally identify an apical tubulin ring (ATR) that colocalises with markers of the conoid in related apicomplexan parasites. This tubulin-containing structure was presumed to be lost in Plasmodium despite its crucial role in motility and invasion in other apicomplexans. Here, U-ExM reveals that a divergent and considerably reduced form of the conoid is actually conserved in Plasmodium species.

A divergent cyclin/cyclin-dependent kinase complex controls the atypical replication of a malaria parasite during gametogony and transmission

Cell cycle transitions are generally triggered by variation in the activity of cyclin-dependent kinases (CDKs) bound to cyclins. Malaria-causing parasites have a life cycle with unique cell-division cycles, and a repertoire of divergent CDKs and cyclins of poorly understood function and interdependency. We show that Plasmodium berghei CDK-related kinase 5 (CRK5), is a critical regulator of atypical mitosis in the gametogony and is required for mosquito transmission. It phosphorylates canonical CDK motifs of components in the pre-replicative complex and is essential for DNA replication. During a replicative cycle, CRK5 stably interacts with a single Plasmodium-specific cyclin (SOC2), although we obtained no evidence of SOC2 cycling by transcription, translation or degradation. Our results provide evidence that during Plasmodium male gametogony, this divergent cyclin/CDK pair fills the functional space of other eukaryotic cell-cycle kinases controlling DNA replication.

Ca2+ signals critical for egress and gametogenesis in malaria parasites depend on a multipass membrane protein that interacts with PKG

Calcium signaling regulated by the cGMP-dependent protein kinase (PKG) controls key life cycle transitions in the malaria parasite. However, how calcium is mobilized from intracellular stores in the absence of canonical calcium channels in Plasmodium is unknown. Here, we identify a multipass membrane protein, ICM1, with homology to transporters and calcium channels that is tightly associated with PKG in both asexual blood stages and transmission stages. Phosphoproteomic analyses reveal multiple ICM1 phosphorylation events dependent on PKG activity. Stage-specific depletion of Plasmodium berghei ICM1 prevents gametogenesis due to a block in intracellular calcium mobilization, while conditional loss of Plasmodium falciparum ICM1 is detrimental for the parasite resulting in severely reduced calcium mobilization, defective egress, and lack of invasion. Our findings suggest that ICM1 is a key missing link in transducing PKG-dependent signals and provide previously unknown insights into atypical calcium homeostasis in malaria parasites essential for pathology and disease transmission.

cGMP homeostasis in malaria parasites-The key to perceiving and integrating environmental changes during transmission to the mosquito

Malaria-causing parasites are transmitted from humans to mosquitoes when developmentally arrested gametocytes are taken up by a female Anopheles during a blood meal. The changes in environment from human to mosquito activate gametogenesis, including a drop in temperature, a rise in pH, and a mosquito-derived molecule, xanthurenic acid. Signaling receptors have not been identified in malaria parasites but mounting evidence indicates that cGMP homeostasis is key to sensing extracellular cues in gametocytes. Low levels of cGMP maintained by phosphodiesterases prevent precocious activation of gametocytes in the human blood. Upon ingestion, initiation of gametogenesis depends on the activation of a hybrid guanylyl cyclase/P4-ATPase. Elevated cGMP levels lead to the rapid mobilization of intracellular calcium that relies upon the activation of both cGMP-dependent protein kinase and phosphoinositide phospholipase C. Once calcium is released, a cascade of phosphorylation events mediated by calcium-dependent protein kinases and phosphatases regulates the cellular processes required for gamete formation. cGMP signaling also triggers timely egress from the host cell at other life cycle stages of malaria parasites and in Toxoplasma gondii, a related apicomplexan parasite. This suggests that cGMP signaling is a versatile platform transducing external cues into calcium signals at important decision points in the life cycle of apicomplexan parasites.

A Plasmodium membrane receptor platform integrates cues for egress and invasion in blood forms and activation of transmission stages

Critical events in the life cycle of malaria-causing parasites depend on cyclic guanosine monophosphate homeostasis by guanylyl cyclases (GCs) and phosphodiesterases, including merozoite egress or invasion of erythrocytes and gametocyte activation. These processes rely on a single GCα, but in the absence of known signaling receptors, how this pathway integrates distinct triggers is unknown. We show that temperature-dependent epistatic interactions between phosphodiesterases counterbalance GCα basal activity preventing gametocyte activation before mosquito blood feed. GCα interacts with two multipass membrane cofactors in schizonts and gametocytes: UGO (unique GC organizer) and SLF (signaling linking factor). While SLF regulates GCα basal activity, UGO is essential for GCα up-regulation in response to natural signals inducing merozoite egress and gametocyte activation. This work identifies a GC membrane receptor platform that senses signals triggering processes specific to an intracellular parasitic lifestyle, including host cell egress and invasion to ensure intraerythrocytic amplification and transmission to mosquitoes.

Efficacy of cancer chemotherapy in relation to synchronization of cortisol rhythm, immune status and psychospiritual profile in metastatic non-small cell lung cancer

BACKGROUND

The prognosis of cancer and the efficacy of the various anticancer therapies depend not only on tumor characteristics, but also on the endocrine and immune status of patients. Moreover, studies have shown that the clinical course of the neoplastic disease is also influenced by the psychospiritual status of patients. It is thus probable that the influence of psychospirituality on tumor growth may be mediated by the immunoneuroendocrine system, as demonstrated by the recent advances in psychoneuroendocrinological research. However, at present there are only few data on the possible link between the psychospiritual status and immunoendocrine functions of cancer patients. This study was carried out to investigate the relationships existing among the psychospiritual profile, cortisol rhythm and lymphocyte number before and after chemotherapy, and the efficacy of chemotherapy itself in advanced cancer patients.

PATIENTS AND METHODS

The study included 30 consecutive metastatic non-small cell lung cancer patients under chemotherapeutic treatment with cisplatin plus gemcitabine. The psychobiological investigations consisted of lymphocyte count, cortisol circadian rhythm, psychological profile using Rorschach test, and spiritual score, as assessed by a specific clinical test for spirituality. The control group consisted of 100 healthy volunteers. The patients who achieved a tumor regression, showed a significantly higher pre-treatment lymphocyte count and significantly lower alteration of the cortisol rhythm with respect to those who had no benefit from chemotherapy. Moreover, the lymphocyte mean number increased during chemotherapy in responder patients, whereas it progressively diminished in those who had disease progression. Lymphocytopenia and alterations of the cortisol rhythm prior to chemotherapy were associated with a loss of the psychosexual identity according the Rorschach test. Moreover, the mean spiritual score was lower in patients than in controls, although the difference was not significant. Finally, a low spiritual score prior to therapy was associated with a higher frequency of lymphocytopenia and cortisol rhythm alteration, as well as with a lower efficacy of chemotherapy itself.

CONCLUSION

This preliminary study would suggest that the psychospiritual status of cancer patients may influence the efficacy of chemotherapy through the immunoneuroendocrine system.

A spiritual approach in the treatment of cancer: relation between faith score and response to chemotherapy in advanced non-small cell lung cancer patients

BACKGROUND

The recent advances in the psychooncological and psychoneuroimmunological investigations of cancer patients has allowed the rediscovery of the importance of spiritual faith in influencing the clinical course of neoplastic disease, not only in terms of supportive care but also as a potential prognostic variable.

MATERIALS AND METHODS

Clinical criteria were worked out to explore the existence of a real status of faith, in an attempt to correlate the degree of faith with the clinical response to chemotherapy, consisting of cisplatin plus gemcitabine, and the overall survival time in a group of 50 metastatic nonsmall cell lung cancer patients.

RESULTS

The tumor response rate achieved in patients with a high degree of faith was significantly higher than in the other group of patients. Moreover, the mean postchemotherapeutic lymphocyte number was significantly higher in the patients with evident spiritual faith than in the other patients. Finally, the percent age of 3-year survival observed in the patients with a high degree of faith was significantly higher than that in the patients with a low faith score.

CONCLUSION

This preliminary study suggests that spiritual faith may positively influence the efficacy of chemotherapy and the clinical course of neoplastic disease, at least in lung cancer, by improving the lymphocyte-mediated anticancer immune response.