The SAR is located apical to the ZA and comprises 2 essential complexes: Crumbs (Crb)/Stardust (Sdt)/PatJ and Bazooka (Baz Par3)/Par6/aPKC. In Drosophila epithelia, membranes are subdivided into 3 domains: the subapical region (SAR), the zonula adherens (ZA), and the septate junctions (SJ) ( 9). It is thought that LKB1's role in cancer may be linked regulation of cell polarity. In mammalian cells, overexpression of LKB1 can induce polarization of membranes in the absence of cell contacts ( 8). In mice, loss of LKB1 leads to embryonic lethality and neural tube defects ( 6), and lbk1 heterozygous mice exhibit intestinal polyps ( 7). LKB1 (Par-4) is essential for the correct distribution of polarity determinants during Caenorhabditis elegans ( 3, 4) and Drosophila ( 5) development. LKB1 (Par-4/XEEK1/STK11) is a serine/threonine kinase ( 1), and most of the identified mutations in PJS patients have inactivating mutations in the kinase domain ( 2). PJS patients are predisposed to develop malignant cancers of epithelial tissue origin throughout their lifetime. Mutations in lkb1 result in Peutz–Jeghers syndrome (PJS), a disease characterized by benign gastrointestinal hamartomatous polyps. These data suggest that in complex tissues, LKB1 acts on an array of targets to regulate cell polarity. Instead, we find that a number of other AMPK-like kinase, such as SIK, NUAK, Par-1, KP78a, and KP78b show phenotypes similar to weak lkb1 loss of function in the eye.
These data suggest that AMPK is not the primary target of LKB1 during eye development. In addition, nutrient deprivation does not reveal a more dramatic polarity phenotype in lkb1 photoreceptors. Unlike lkb1 mutants, ampk retinas do not show elongated rhabdomeres or expansion of apical and junctional markers into the basolateral domain. Surprisingly, we find LKB1 does not act primarily through AMPK to regulate cell polarity in the retina. We show that adherens junctions expand and apical, junctional, and basolateral domains mix in lkb1 mutants. To determine whether this simple model of how LKB1 regulates cell polarity has relevance to complex tissues, we examined lkb1 mutants in the Drosophila eye. Recent studies propose that LKB1 acts primarily through the AMP kinase to establish and/or maintain cell polarity. Biochemical analysis indicates that LKB1 can phosphorylate and activate a family of AMPK- like kinases, however, the precise contribution of these kinases to the establishment and maintenance of cell polarity is still unclear. Loss of lkb1 leads to a cancer predisposition, known as Peutz–Jeghers Syndrome. So, let's discuss.The serine–threonine kinase LKB1 regulates cell polarity from Caenorhabditis elegans to man. But when the sartorial gaffes in question relate to purposeful trolling, political insensitivity, or even sheer ignorance - Melania Trump's "I Really Don't Care, Do U?" jacket falls into at least one of these categories - they become part of a larger political discussion. Women of the White House are often scrutinized for what they wear, and some of this scrutiny has, in turn, been scrutinized for its sexism. Fashion has continued to be a contentious subject in the conversation surrounding the First Daughter, particularly when she has worn outfits that have been deemed inappropriate or insensitive to political events that have directly involved the Trump administration. Within weeks of the 45th president's inauguration, Nordstrom announced it would pull Ivanka Trump clothes, shoes, and accessories from its shelves, citing poor performance.
Once Donald Trump entered the White House, the Ivanka Trump brand fell into the crosshairs of a storm of controversies, including ethical concerns and conflict-of-interest accusations.
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