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Cervical cancer (CC) is one of the most frequent cancers in women worldwide. The epithelial-mesenchymal transition (EMT) and the extracellular release of TGF-β are phenomena typically associated with different tumorigenic processes, including tumour cell proliferation and metastatization. Specific human microRNAs (miRNAs; miRs) involved in these tumorigenic processes have been identified, becoming important diagnostic and prognostic markers, and even potential therapeutic targets. In parallel, different studies have also shown that plant miRNAs can mediate a cross-kingdom regulation (CKR) of mammalian genes and modulate host's gene expression under pathological conditions, restoring the regulatory activity of endogenous miRNAs lost in cancer. In our previous studies, the miRNome from Moringa oleifera Lam. (henceforth moringa or mol) has been sequenced, showing the presence of several conserved miRNAs in the plant kingdom, whose ability to differentially regulate proliferation and apoptosis in healthy and cancer cells has been demonstrated. Furthermore, the effects of mol-miR treatment on tumorigenesis and EMT have been proved in liver tumour cells. According to these premises, we here investigated the proteomic profile of CC-derived HeLa cells exposed to a mol-miRNA pool, demonstrating the down-representation of specific factors involved in tumorigenesis. The treatment with plant miRs was able to modulate proteins involved in several biological processes linked to EMT. Furthermore, it reduced the expression of TGF-β and significantly inhibited cell motility, as observed following Scratch test and cell viability measurements, with a significant increase of apoptotic events. In conclusion, our results suggest and pave the way for the development of new potential therapeutic approaches based on CKR mediated by plant miRNAs for contrasting human cervical cancer, even in the form of adjuvants to classic treatments for limiting their side effects.

Although an increasing body of evidence indicates that plant MAP kinases are involved in a number of cellular processes, such as cell cycle regulation and cellular response to abiotic stresses, hormones and pathogen attack, very little is known about their biochemical properties and regulation mechanism. In this paper we report on the identification and characterization of a novel member of the MAP kinase family from maize, ZmMPK6. The amino acid sequence reveals a high degree of identity with group D plant MAP kinases. Recombinant ZmMPK6, expressed in Escherichia coli, is an active enzyme able to autophosphorylate. Remarkably, ZmMPK6 interacts in vitro with GF14-6, a maize 14-3-3 protein and the interaction is dependent on autophosphorylation. The interacting domain of ZmMPK6 is on the C-terminus and is comprised between amino acid 337 and amino acid 467. Our results represent the first evidence of an interaction between a plant MAP kinase and a 14-3-3 protein. Possible functional roles of this association in vivo are discussed.

The H+-ATPase is a key enzyme for the establishment and maintenance of plasma membrane potential and energization of secondary active transport in the plant cell. The phytotoxin fusicoccin induces H+-ATPase activation by promoting the association of 14-3-3 proteins. It is still unclear whether 14-3-3 proteins can represent natural regulators of the proton pump, and factors regulating 14-3-3 binding to the H+-ATPase under physiological conditions are unknown as well. In the present study in vivoand in vitroevidence is provided that 14-3-3 proteins can associate with the H+-ATPase from maize roots also in a fusicoccin-independent manner and that the interaction depends on the phosphorylation status of the proton pump. Furthermore, results indicate that phosphorylation of H+-ATPase influences also the fusicoccin-dependent interaction of 14-3-3 proteins. Finally, a protein phosphatase 2A able to impair the interaction between H+-ATPase and 14-3-3 proteins was identified and partially purified from maize root.

Purified preparations of FC receptors from maize, obtained under non-denaturing conditions, showed in SDS-PAGE two doublets of proteins with an apparent molecular mass of 30 and 90 kDa. In this paper the isolation of the 30 kDa protein, its identification as a 14-3-3-like protein, as well as its immunological detection in partially-purified FC-receptor preparations from bean and spinach are described. The 14-3-3 proteins have biochemical properties consistent with potential signalling roles, and their presence in highly purified FC-receptor preparations suggests that they may be involved in FC- signal transduction. Photoaffinity labelling experiments demonstrating that the protein at 90 kDa binds FC are also presented. The evidence presented taken as a whole, suggests the occurrence in maize of a protein complex for FC perception and signal transduction.

The activity of ‘P-type’ ATPases is modulated through the C-terminal autoinhibitory domain. The molecular bases of this regulation are unknown. Their understanding demands functional and structural studies on the activated purified enzyme. In this paper the plasma membrane H +-ATPase from maize roots activated in vivo by fusicoccin was solubilised and fractionated by anion-exchange HPLC. Results showed that the H +-ATPase separated from fusicoccin receptors retained fusicoccin activation and that it was more evident after enzyme insertion into liposomes. These data suggest that fusicoccin stimulation does not depend on a direct action of the fusicoccin receptor on the H +-ATPase, but rather, fusicoccin brings about a permanent modification of the H +-ATPase which very likely represents a general regulatory mechanism for ‘P-type’ ATPases.

Biochemical properties of fusicoccin receptors are strongly influenced by the phospholipid environment. In this report we have studied the effect of different exogenous phospholipases on fusicoccin binding ability of both plasma membrane and solubilised receptors. Among the phospholipases tested only phospholipase A 2; showed an inhibitory effect on fusicoccin binding. In particular, the influence of this enzyme on the time course and reversibility of the fusicoccin binding reaction was studied. The inhibitory effect of phospholipase A 2was the consequence of fatty acid release. The usual fatty acids of plasma membrane phospholipids were active in inhibiting the interaction of fusicoccin with its receptors. It is concluded that a phospholipid associated to the fusicoccin receptor might play a significant role in the modulation of binding.

Biochemical properties of fusicoccin receptors are strongly influenced by the phospholipid environment. In this report we have studied the effect of different exogenous phospholipases on fusicoccin binding ability of both plasma membrane and solubilised receptors. Among the phospholipases tested only phospholipase A2; showed an inhibitory effect on fusicoccin binding. In particular, the influence of this enzyme on the time course and reversibility of the fusicoccin binding reaction was studied. The inhibitory effect of phospholipase A2was the consequence of fatty acid release. The usual fatty acids of plasma membrane phospholipids were active in inhibiting the interaction of fusicoccin with its receptors. It is concluded that a phospholipid associated to the fusicoccin receptor might play a significant role in the modulation of binding.

The activity of ‘P‐type’ ATPases is modulated through the C‐terminal autoinhibitory domain. The molecular bases of this regulation are unknown. Their understanding demands functional and structural studies on the activated purified enzyme. In this paper the plasma membrane H+‐ATPase from maize roots activated in vivo by fusicoccin was solubilised and fractionated by anion‐exchange HPLC. Results showed that the H+‐ATPase separated from fusicoccin receptors retained fusicoccin activation and that it was more evident after enzyme insertion into liposomes. These data suggest that fusicoccin stimulation does not depend on a direct action of the fusicoccin receptor on the H+‐ATPase, but rather, fusicoccin brings about a permanent modification of the H+‐ATPase which very likely represents a general regulatory mechanism for ‘P‐type’ ATPases.