Actin retrograde flow controls natural killer cell response by regulating the conformation state of SHP‐1

Natural killer (NK) cells are a powerful weapon against viral infections and tumor growth. Although the actin–myosin (actomyosin) cytoskeleton is crucial for a variety of cellular processes, the role of mechanotransduction, the conversion of actomyosin mechanical forces into signaling cascades, was never explored in NK cells. Here, we demonstrate that actomyosin retrograde flow (ARF) controls the immune response of primary human NK cells through a novel interaction between β‐actin and the SH2‐domain‐containing protein tyrosine phosphatase‐1 (SHP‐1), converting its conformation state, and thereby regulating NK cell cytotoxicity. Our results identify ARF as a master regulator of the NK cell immune response. Since actin dynamics occur in multiple cellular processes, this mechanism might also regulate the activity of SHP‐1 in additional cellular systems.     

Quantitative studies on the regeneration of myelinated nerve fibers. II. Variations of the number and size of regenerating nerve fibers after localized crushing or total section]

1. The number and size of myelinated nerve fibers have been determined at standard levels, in the nerve to medial head of right and left gastrocnemius muscles of 112 rats in which the left sciatic nerve had suffered an experimental lesion according one of the following four modalities: localized crushing, total section followed or not by suture and resection of a nervous segment of about 1 cm. 2. In the nerve to medial head of right gastrocnemius muscle (contralateral nerve used as control), the number of myelinated fibers decreased in average to 10% after crushing, 5% or 4% after section followed or not by suture. However, an increase of 6% was observed after resection. The mean values of the mean diameters showed a decrease of 8% after crushing and 5% after section without suture. This value did not seem to be affected by section followed by immediate suture and after resection, it increased of 11%. On the whole, male rats appeared to be more sensitive than female to the effects of the operation. 3. The nerves of 12 rats have been observed from 15 to 334 days after resection of about 1 cm of sciatic nerve. The 20% of the regenerating myelinated nerve fibers which have succeeded to cross over such a distance had a distribution which remained unimodal; the diameter of the large fibres did not exceed 8 micronm. 4. 34 rats have been sacrificed from 15 to 715 days after sciatic nerve section which was not followed by suture. The number of myelinated nerve fibers became normal again during the 4th month and reached afterwards a mean value of 130%, with very marked variations. The nerve fibre distribution was most frequently unimodal, but may came bimodal one year after the operation in certain nerves. Their mean diameter never exceeded 60% of the normal. 5. The nerves of 34 rats have been examined from 15 to 720 days after section and immediate suture. The number of myelinated nerve fibers returned to normal during the second month and increased afterwards to an average of 150% with very important variations. The nerve fiber distribution was generally unimodal, but may become bimodal 7 months after the operation. Their mean diameter reached only 50 to 55% of the normal. 6. 32 rats have been sacrificed from 10 to 720 rats after a localized crushing. The number of myelinated nerve fibers come back to normal during the 4th week and later increased up to a mean of 115%. Their distribution became early bimodal from the 97th day onwards. Although, their mean diameter nerver exceeded 80% of the normal, the histograms of the regenerating nerve and of the control nerve could be almost superposed during the second year.     

Detection and Identification of Two Phytoplasmas (16SrIII‐B and 16SrXII‐A) From Alfalfa (Medicago sativa) in Serbia

Plants of alfalfa (Medicago sativa) exhibiting general stunting, proliferation and phyllody associated with leaf yellowing and reddening were observed in three localities of Central Serbia. Phytoplasma strains belonging to 16SrIII‐B and 16SrXII‐A groups were detected and identified by RFLP and sequence analysis of 16S rDNA. Stolbur phytoplasma tuf gene RFLP analysis showed the presence of the TufAY‐b‐type phytoplasma subgroup in 80% of symptomatic samples. This is the first report of 16SrIII‐B and 16SrXII‐A phytoplasma groups affecting alfalfa in Serbia.     

How Does It Kill?: Understanding the Candidacidal Mechanism of Salivary Histatin 5

Histatins are salivary cationic peptides that provide the first line of defense against oral candidiasis caused by Candida albicans. This minireview presents a critical evaluation of our knowledge of the candidacidal mechanism of histatin 5 (Hst 5). Hst 5 is the most potent among all histatin family members with regard to its antifungal activity. The mode of action of Hst 5 has been a subject of intense debate. Unlike other classical host innate immune proteins, pore formation or membrane lysis by Hst 5 has largely been disproven, and it is now known that all targets of Hst 5 are intracellular. Hst 5 binds C. albicans cell wall proteins (Ssa1/2) and glycans and is taken up by the cells through fungal polyamine transporters in an energy-dependent manner. Once inside the fungal cells, Hst 5 may affect mitochondrial functions and cause oxidative stress; however, the ultimate cause of cell death is by volume dysregulation and ion imbalance triggered by osmotic stress. Besides these diverse targets, a novel mechanism based on the metal binding abilities of Hst 5 is discussed. Finally, translational approaches for Hst 5, based on peptide design and synergy with other known drugs, are considered a step forward for bench-to-bed application of Hst 5.     

SDS-polyacrylamide gel electrophoresis of membrane proteins: effect of phospholipids

Under the conditions described in this report, it was found that the occurrence of phospholipids in membrane samples has no artifactual impact on the subsequent separation and visualization of membrane proteins in SDS-polyacrylamide gels stained with Coomassie Blue.