Lectins of the <Emphasis Type="Italic">Nicotiana tabacum</Emphasis> pollen grain walls stimulating in vitro pollen germination

Proteins diffusing from tobacco pollen grains into external medium, being inactivated by low temperature (0°C), were shown to stimulate pollen germination in vitro. Fractionation of these proteins by affinity chromatography using α-D-methylmannopyranoside (MMP) immobilized on agarose resulted in the isolation of lectins stimulating germination. The mol wts of these lectins were estimated by SDS-PAGE as 58, 69, and 74 kD. A stimulatory effect of these lectins was determined by their specific interaction with carbohydrate determinants because a competitive sugar (0.3 M MMP) suppressed completely lectin effect on germination. Polyvalent lectins capable of erythrocyte agglutination were also found among diffused proteins. These lectins are glycoproteins with Glu/Man carbohydrate determinants. MMP did not affect their capability of agglutination. This finding permits a conclusion that pollen grain wall contains lectins differing in their carbohydrate specificity.     

Eph family receptors as therapeutic targets

Anti-angiogenic therapy is currently a commonly accepted and rapidly developing approach in oncology and other pathologies linked to aberrant neovascularization. Discovery and validation of additional molecular targets in angiogenesis is needed due to the limitations of the existing clinical therapeutics inhibiting activity of vascular endothelial growth factor (VEGF) and its receptors. A brief review of normal and pathological biological functions of the Eph family of receptor tyrosine kinases and their ephrin ligands is presented, and the approaches to developing therapeutics with anti- and pro-angiogenic and anti-tumor activity based on selective molecular modulation of Eph-ephrin signaling pairs are discussed. Functional roles of Eph-kinases and ephrins in such mechanisms of carcinogenesis as cell proliferation and invasion are also addressed.