Role of the hydrophobic domain in targeting caveolin-1 to lipid droplets

Although caveolins normally reside in caveolae, they can accumulate on the surface of cytoplasmic lipid droplets (LDs). Here, we first provided support for our model that overaccumulation of caveolins in the endoplasmic reticulum (ER) diverts the proteins to nascent LDs budding from the ER. Next, we found that a mutant H-Ras, present on the cytoplasmic surface of the ER but lacking a hydrophobic peptide domain, did not accumulate on LDs. We used the fact that wild-type caveolin-1 accumulates in LDs after brefeldin A treatment or when linked to an ER retrieval motif to search for mutants defective in LD targeting. The hydrophobic domain, but no specific sequence therein, was required for LD targeting of caveolin-1. Certain Leu insertions blocked LD targeting, independently of hydrophobic domain length, but dependent on their position in the domain. We propose that proper packing of putative hydrophobic helices may be required for LD targeting of caveolin-1

The Dually Acylated NH2-terminal Domain of Gi1α Is Sufficient to Target a Green Fluorescent Protein Reporter to Caveolin-enriched Plasma Membrane Domains: PALMITOYLATION OF CAVEOLIN-1 IS REQUIRED FOR THE RECOGNITION OF DUALLY ACYLATED G-PROTEIN α SUBUNITS IN VIVO

Here we investigate the molecular mechanisms that govern the targeting of G-protein α subunits to the plasma membrane. For this purpose, we used Gi1α as a model dually acylated G-protein. We fused full-length Gi1α or its extreme NH2-terminal domain (residues 1–32 or 1–122) to green fluorescent protein (GFP) and analyzed the subcellular localization of these fusion proteins. We show that the first 32 amino acids of Gi1α are sufficient to target GFP to caveolin-enriched domains of the plasma membrane in vivo, as demonstrated by co-fractionation and co-immunoprecipitation with caveolin-1. Interestingly, when dual acylation of this 32-amino acid domain was blocked by specific point mutations (G2A or C3S), the resulting GFP fusion proteins were localized to the cytoplasm and excluded from caveolin-rich regions. The myristoylated but nonpalmitoylated (C3S) chimera only partially partitioned into caveolin-containing fractions. However, both nonacylated GFP fusions (G2A and C3S) no longer co-immunoprecipitated with caveolin-1. Taken together, these results indicate that lipid modification of the NH2-terminal of Gi1α is essential for targeting to its correct destination and interaction with caveolin-1. Also, a caveolin-1 mutant lacking all three palmitoylation sites (C133S, C143S, and C156S) was unable to co-immunoprecipitate these dually acylated GFP-G-protein fusions. Thus, dual acylation of the NH2-terminal domain of Gi1α and palmitoylation of caveolin-1 are both required to stabilize and perhaps regulate this reciprocal interaction at the plasma membrane in vivo. Our results provide the first demonstration of a functional role for caveolin-1 palmitoylation in its interaction with signaling molecules

Antiadhesive Role of Apical Decay-accelerating Factor (CD55) in Human Neutrophil Transmigration across Mucosal Epithelia

Neutrophil migration across mucosal epithelium during inflammatory episodes involves the precise orchestration of a number a cell surface molecules and signaling pathways. After successful migration to the apical epithelial surface, apically localized epithelial proteins may serve to retain PMN at the lumenal surface. At present, identification of apical epithelial ligands and their PMN counter-receptors remain elusive. Therefore, to define the existence of apical epithelial cell surface proteins involved in PMN–epithelial interactions, we screened a panel of antibodies directed against epithelial plasma membranes. This strategy identified one antibody (OE-1) that both localized to the apical cell membrane and significantly inhibited PMN transmigration across epithelial monolayers. Microsequence analysis revealed that OE-1 recognized human decay-accelerating factor (DAF, CD55). DAF is a highly glycosylated, 70–80-kD, glycosyl-phosphatidyinositol–linked protein that functions predominantly as an inhibitor of autologous complement lysis. DAF suppression experiments using antisense oligonucleotides or RNA interference revealed that DAF may function as an antiadhesive molecule promoting the release of PMN from the lumenal surface after transmigration. Similarly, peptides corresponding to the antigen recognition domain of OE-1 resulted in accumulation of PMN on the apical epithelial surface. The elucidation of DAF as an apical epithelial ligand for PMN provides a target for novel anti-inflammatory therapies directed at quelling unwanted inflammatory episodes

“It feels like someone is hammering my feet”: Understanding pain and its management from the perspective of people with Multiple Sclerosis

Background: Pain affects around 63% of people with multiple sclerosis (pwMS). Biomedical treatments demonstrate limited efficacy. More research is needed to understand pain from the individual’s perspective in order to better inform a patient-centred approach that improves engagement, self-management and outcome. Objective: The objective of this paper is to explore pwMS’ experience and responses to pain, and their perspectives on pain management. Methods: Twenty-five in-depth, semi-structured telephone interviews were conducted. Interviews were audiotaped, transcribed and analysed using an inductive thematic analysis approach with elements of grounded theory. Results: Key themes included vivid descriptions of pain and beliefs that pain is unpredictable, a sign of damage and may worsen. Anger was a common emotional response. Two dominant pain management themes emerged: one related to pain reduction and another to acceptance. Those focusing on pain reduction appeared to engage in cycles in which they struggled with symptoms and experienced continued distress. Conclusion: Findings identify pain-related beliefs, emotional reactions and disparate pain-management attitudes. All may influence pwMS’ responses to pain and what they ask of their clinicians. Uncovering pwMS’ personal beliefs about pain, and introducing a broader biopsychosocial understanding of pain in the clinical context, may provide opportunities to rectify potentially unhelpful management choices and enhance pain acceptance

Human genes for three complement components that regulate the activation of C3 are tightly linked

Two groups of complement components are involved in the activation of C3. The first includes C2, factor B (B), C4, and C3, i.e., the structural components of the C3 convertases of the classical and alternative pathways. The second contains the regulatory proteins C4-binding protein (C4-bp), factor H (H), the C3b/C4b receptor (CRI or C3bR), and, probably, the decay-accelerating factor (DAF) and gp45-70. C2, C4, and factor B are encoded by a cluster of genes inside the major histocompatibility complex (MHC), 1 a genetic association that is consistently found in mammalian species (reviewed in 1 and 2). The mechanisms leading to that linkage and its evolutionary stability are unclear, as are its functional and genetic consequences. Study of the linkage relationships of other genes that code for proteins involved in the activation of C3 is, therefore, of considerable interest. We have recently demonstrated genetics variants of C4-bp (3), H (4), and C3bR (5, 6) in humans and have reported that the loci coding for C4-bp and C3bR are very closely linked (7). We proposed (7) the hypothesis that a cluste