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cell combination drug delivery ---New technology for treating AML

Posted by star on 2018-11-07 22:05:41

    on October 29th ,2018,“Conjugation of haematopoietic stem cells and platelets decorated with anti-PD-1 antibodies augments anti-leukaemia efficacy”was published in Nature Biomedical Engineering. The researchers proposed a "cell combination drug delivery" (CCDD) technology: two different cells are glued together to target drug delivery.It has been verified on animal models that the anti-cancer drug can be delivered to the deep bone marrow to enhance the efficacy of killing cancer cells and significantly inhibit recurrence.
    This technology is currently targeted at acute myeloid leukemia (AML). This is a cancer that develops in the bone marrow. Generally speaking, for AML patients, the usual treatment is chemotherapy, but its effect is not so ideal. Usually because some cancer cells are hidden in the bone marrow, chemotherapy does not "deep into the bone marrow.
    CCDD technology is the first treatment to connect two different cells together. Among them, one type of cell is a platelet which is used to deliver an immunotherapy drug PD-1 antibody. These drugs can find cancer cells and destroy their defense systems. Another type of cell is a hematopoietic stem cell(HSC). HSC are like a signal pointing to the bone marrow. Once stem cells bring cell combinations (ie, stem cells and platelets) to the bone marrow, platelets can be activated, releasing drugs and exerting anticancer effects.
    The researchers injected HSC-platelet-aPD-1 conjugates into these leukemia mouse models.
    After 3 weeks of treatment, the cancer lesions in the mice were effectively reduced. In many control groups, cancer has intensified.In terms of survival rate, nearly 90% of the mice receiving the new treatment lived for more than 80 days.Mice in the control group can only live up to 40 days. This therapy not only treats patients individually, but can also be combined with chemo......

The Lac repressor is a dimer of dimers

Posted by star on 2018-11-07 18:13:24

    Mitchell Lewis and coworkers obtained the crystal structure for the Lac repressor bound to IPTG or lac DNA in 1996. It shows the structure of one of the four identical Lac repressor subunits. As indicated in the figure, the monomer has four distinct functional units:
    1. N-terminal domain or headpiece (residues 1-45) binds lac operator DNA. A helix-turn-helix motif within the head-piece recognizes and binds appropriate operator DNA. Helix-turn-helix motifs, which are often present in proteins that bind to DNA, consist of two short α-helical segments containing between 7 and 9 residues that are separated by a β-turn (a tight turn involving four amino acid residues). One of the two α-helices, designated the recognition helix, is positioned in the major groove of the DNA so that amino acid residues within this helix make specific contacts with bases in the DNA. The other helix, which is designated the stabilization helix, helps to stabilize the complex.
    2. The hinge region (residues 46-62), which joins the N-terminal headpiece to the core domain, is disordered in the absence of DNA but folds into an α-helix upon binding to operator DNA. Two hinge helices in a Lac repressor dimer associate through van der Waals interactions and the paired hinge helices bind to the center of the lac operator in the minor groove and bend the DNA.
    3. The ligand binding or core domain (residues 62-340) is divided into an N-terminal sub-domain and a C-terminal sub-domain. The two kinds of sub-domain have similar folding patterns, Weak non-covalent interactions between N-terminal sub-domains as well as between C-terminal sub-domains make important contributions to Lac repressor dimer formation. IPTG fits in a pocket between the two sub-domains in each polypeptide.
    4. The tetramerization helix (residues 341-357) associates with corresponding regions of the......

Escherichia coli prefer glucose or lactose

Posted by star on 2018-11-07 18:08:38

    The function of β-galactosidase in lactose metabolism is to hydrolyze lactose to form glucose and galactose. If the growth medium contains both glucose and lactose, then in the interest of efficiency there is no need for a cell to turn on the lac operon. Experiments performed by Monod in the mid-1940s demonstrated that cells behave according to this logic. E. coli cells incubated in the presence of glucose and lactose do not start to make β-galactosidase until all of the exogenous glucose is consumed. These findings were later extended to lactose permease and transacetylase, the two other proteins specified by the lac operon. As also the reason that lactose enzymes are not made when glucose is present is that no lac NRNA is made. Transcription-level inhibition of the lactose enzymes and a variety of other inducible enzymes by glucose (or other readily used carbon sources) is called catabolite repression.

The lac operon

Posted by star on 2018-11-06 18:37:48

    After the lac operon was sequenced, it eventually became clear that it has two additional operators. The original operator with its center of symmetry at position + 11 is now designated lacO1. Auxiliary operators lacO2 and lacO3 have their centers of symmetry at positions+412 and-82, respectively. Thus, lacO3 is upstream of the lac promoter while lacO2 is located in lacZ.
    The discoveries of lacO2 and lacO3 led investigators to ask whether these auxiliary operators play a role in lac operon regulation. Millier-Hill and coworkers performed a series of genetic experiments that answered this question. Their approach was to alter one or more lac operators and then determine the alteration's effect on repression. Point mutations in taco, caused a 5-to 50-fold decrease in repression, but some repression was still observed. Destruction of either lacO2 or lacO3 caused a twofold decrease in repression and destruction of both auxiliary operators caused a 70-fold decrease in repression. The ability to repress the lac system was completely lost in cells in which lacO1, and either of the auxiliary opera-tors were destroyed. These re X indicate that lacO1 plays a major role in repression but the two auxiliary operators also make important contributions. We will now examine the structure of the Lac repressor to see how it interacts with the lac operators.

A new method for blocking cancer immunosuppression

Posted by star on 2018-11-06 17:52:10

    In a new study, Belgian researchers elucidated the three-dimensional structure of a protein complex that suppresses immune responses on the cell surface. They also discovered how antibodies can block this protein complex and its downstream induced immunosuppression. The antibodies may be used to activate the immune response against tumor cells in cancer patients, thereby triggering immune cells to destroy the tumor. The results of the study were published in Science on October 25, 2018, entitled "Structure based on potential TGF-β1 expression and GARP activation of human regulatory T cells."

    Regulatory T cells (Tregs) are immunosuppressive cells that, under normal conditions, resist excessive immune responses in the body to prevent autoimmune diseases. However, in cancer patients, they play a detrimental role by inhibiting the immune response against tumor cells. Treg cells exert their effects by producing a messenger protein called TGF-β. This messenger transmits an inhibitory signal to nearby immune cells, especially those that should destroy tumors in cancer patients. The way which Treg cells produce TGF-β is complex and finely regulated because TGF-β is very efficient and must be tightly controlled.
    3 years ago, the researchers found that TGF-β is released from a protein called GARP on the surface of Treg cells. It is possible to block the release of TGF-β from GARP using specific antibodies.

    The researchers resolved the three-dimensional structure of a protein complex assembled by GARP and TGF-β. The structure of GARP is similar to horseshoe, and TGF-β straddles this horseshoe structure. The two molecules are assembled so complexly that TGF-β itself contributes to the formation of the horseshoe-shaped structure of GARP. In this protein complex, this blocking antibody binds to GARP and TGF-β. It seems to bind the t......

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