Significance This study uses large-scale news media and social media data to show that nationwide Black Lives Matter (BLM) protests occur concurrently with sharp increases in public attention to components of the BLM agenda. We also show that attention to BLM and related concepts is not limited to these brief periods of protest but is sustained after protest has ceased. This suggests that protest events incited a change in public awareness of BLM’s vision of social change and the dissemination of antiracist ideas into popular discourse.

Political bots are social media algorithms that impersonate political actors and interact with other users, aiming to influence public opinion. This study investigates the ability to differentiate bots with partisan personas from humans on Twitter. Our online experiment ( N = 656) explores how various characteristics of the participants and of the stimulus profiles bias recognition accuracy. The analysis reveals asymmetrical partisan-motivated reasoning, in that conservative profiles appear to be more confusing and Republican participants perform less well in the recognition task. Moreover, Republican users are more likely to confuse conservative bots with humans, whereas Democratic users are more likely to confuse conservative human users with bots. We discuss implications for how partisan identities affect motivated reasoning and how political bots exacerbate political polarization.

CX 3 CL1, a chemokine with transmembrane and soluble species, plays a key role in inflammation by acting as both chemoattractant and adhesion molecule. CX 3 CL1 is the only chemokine known to undergo constitutive internalization, raising the possibility that dynamic equilibrium between the endocytic compartment and the plasma membrane critically regulates the availability and processing of CX 3 CL1 at the cell surface. We therefore investigated how transmembrane CX 3 CL1 is internalized. Inhibition of dynamin using a nonfunctional allele or of clathrin using specific small interfering RNA prevented endocytosis of the chemokine in CX 3 CL1-expressing human ECV-304 cells. Perusal of the cytoplasmic domain of CX 3 CL1 revealed two putative adaptor protein-2 (AP-2)-binding motifs. Accordingly, CX 3 CL1 co-localized with AP-2 at the plasma membrane. We generated a mutant allele of CX 3 CL1 lacking the cytoplasmic tail. Deletion of the cytosolic tail precluded internalization of the chemokine. We used site-directed mutagenesis to disrupt AP-2-binding motifs, singly or in combination, which resulted in diminished internalization of CX 3 CL1. Although CX 3 CL1 was present in both superficial and endomembrane compartments, ADAM10 (a disintegrin and metalloprotease 10) and tumor necrosis factor-converting enzyme, the two metalloproteases that cleave CX 3 CL1, localized predominantly to the plasmalemma. Inhibition of endocytosis using the dynamin inhibitor, Dynasore, promoted rapid metalloprotease-dependent shedding of CX 3 CL1 from the cell surface into the surrounding medium. These findings indicate that the cytoplasmic tail of CX 3 CL1 facilitates its constitutive clathrin-mediated endocytosis. Such regulation enables intracellular storage of a sizable pool of presynthesized CX 3 CL1 that protects the chemokine from degradation by metalloproteases at the plasma membrane.Inflammation is marked by the migration of circulating leukocytes into sites of injury, a process that occurs via a series of coordinated interactions between leukocytes and endothelial or epithelial cells. Central to this process are chemokines, a family of low molecular weight proteins that can attract leukocytes bearing the complementary receptors. When engagement of the chemokine receptor occurs, the leukocyte becomes activated and is induced to firmly adhere to the inflamed endothelium. These initial steps culminate in diapedesis of the leukocyte across the endothelium and migration into the injured tissue. The local complement of chemokines elaborated is organ-specific and varies with the type of inflammation present. In addition, specific leukocyte subsets also bear distinct chemokine receptors. In this way, chemokines and chemokine receptors confer organ specificity to leukocyte migration and help to "fine-tune" the nature of the observed inflammatory response.Among the 40 chemokines identified so far, CX 3 CL1 is one of only two that have a transmembrane structure (1, 2). The chemokine domain of CX 3 CL1 binds to its complementary receptor, CX 3...

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