Asymmetric Evolution of Protein Domains in the Leucine-Rich Repeat Receptor-Like Kinase Family of Plant Signaling Proteins

The coding sequences of developmental genes are expected to be deeply conserved, with cis-regulatory change driving the modulation of gene function. In contrast, proteins with roles in defense are expected to evolve rapidly, in molecular arms races with pathogens. However, some gene families include both developmental and defense genes. In these families, does the tempo and mode of evolution differ between genes with divergent functions, despite shared ancestry and structure? The leucine-rich repeat receptor-like kinase (LRR-RLKs) protein family includes members with roles in plant development and defense, thus providing an ideal system for answering this question. LRR-RLKs are receptors that traverse plasma membranes. LRR domains bind extracellular ligands; RLK domains initiate intracellular signaling cascades in response to ligand binding. In LRR-RLKs with roles in defense, LRR domains evolve faster than RLK domains. To determine whether this asymmetry extends to LRR-RLKs that function primarily in development, we assessed evolutionary rates and tested for selection acting on 11 subfamilies of LRR-RLKs, using deeply sampled protein trees. To assess functional evolution, we performed heterologous complementation assays in Arabidopsis thaliana (Arabidopsis). We found that the LRR domains of all tested LRR-RLK proteins evolved faster than their cognate RLK domains. All tested subfamilies of LRR-RLKs had strikingly similar patterns of molecular evolution, despite divergent functions. Heterologous transformation experiments revealed that multiple mechanisms likely contribute to the evolution of LRR-RLK function, including escape from adaptive conflict. Our results indicate specific and distinct evolutionary pressures acting on LRR versus RLK domains, despite diverse organismal roles for LRR-RLK proteins.

A tumor-infiltrating lymphocyte from a melanoma metastasis with decreased expression of melanoma differentiation antigens recognizes MAGE-12

Twenty separate tumor infiltrating lymphocyte (TIL) bulk cultures and a tumor cell line were originated simultaneously from a fine needle aspiration biopsy of a metastasis in a patient with melanoma (F001) previously immunized with the HLA-A*0201-associated gp100:209-217(210 M) peptide. None of the TIL recognized gp100. However, 12 recognized autologous (F001-MEL) and allogeneic melanoma cells expressing the HLA haplotype A*0201, B*0702, Cw*0702. Further characterization of F001-MEL demonstrated loss of gp100/PMel17, severely decreased expression of other melanoma differentiation Ags and retained expression of tumor-specific Ags. Transfection of HLA class I alleles into B*0702/Cw*0702-negative melanoma cell lines identified HLA-Cw*0702 as the restriction element for F001-TIL. A cDNA library from F001-MEL was used to transfect IFN-alpha-stimulated 293 human embryonal kidney (293-HEK) cells expressing HLA-Cw*0702. A 100-gene pool was identified that induced recognition of 293-HEK cells by F001-TIL. Subsequent cloning of the pool identified a cDNA sequence homologous, except for one amino acid (aa 187 D-->A), to MAGE-12. Among 25 peptide sequences from MAGE-12 with the HLA-Cw*0702 binding motif, MAGE-12:170-178 (VRIGHLYIL) induced IFN-gamma release by F001-TIL when pulsed on F001-EBV-B cells at concentrations as low as 10 pg/ml. Peptide sequences from MAGE-1, 2, 3, 4a, and 6 aligned to MAGE-12:170-178 were not recognized by F001-TIL. In summary a TIL recognizing a MAGE protein was developed from an HLA-A*0201 expressing tumor with strongly reduced expression of melanoma differentiation Ags. Persisting tumor-specific Ag expression maintained tumor immune competence suggesting that tumor-specific Ags/melanoma differentiation Ags may complement each other in the context of melanoma Ag-specific vaccination.

A mutation in integrase can compensate for mutations in the simian immunodeficiency virus att site

Sequences at the left terminus of U3 in the left long terminal repeat (LTR) and at the right terminus of U5 in the right LTR are important for integration of retroviral DNA. In the infectious pathogenic molecular clone of simian immunodeficiency virus strain mac239 (SIVmac239), 10 of the 12 terminal base pairs form an imperfect inverted repeat structure (5' TGGAAGGGATTT 3' [nucleotides 1 to 12] and 3' ACGATCCCTAAA 5' [nucleotides 10279 to 10268]). Nineteen different mutant forms of SIVmac239 proviral DNA with changes at one or more of the positions in each of the 12-terminal-base-pair regions were constructed. Viral replication was severely or completely compromised with nine of these mutants. Revertants appeared 40 to 50 days after transfection in two independent experiments with mutant 7, which contained changes of AGG to TAC at positions 5 to 7 in U3 and TCC to GAA at positions 10275 to 10273 in U5. Virus produced at these times from mutant 7 transfection replicated upon reinfection with only a slight delay when compared to the wild type. Sequence analysis of the LTR and integrase regions from infected cultures revealed two predominant changes: G to A at position 10275 in U5 and Glu to Lys at position 136 in integrase. Derivatives of clone 7 in which these changes were introduced individually and together were constructed by site-specific mutagenesis. Each change individually restored replication capacity only partially. However, the combination of both mutations restored replicative capacity to that of the original revertants. These results indicate that changes in integrase can compensate for mutations in the terminal nucleotides of the SIV LTR. The results further indicate that resistance to integrase inhibitors may include both integrase and LTR mutations.

Nerve growth factor promotes neurite outgrowth in guinea pig myenteric plexus ganglia

Nerve growth factor (NGF) has important developmental actions in both central and peripheral nervous systems. Primary cultures of neonatal guinea pig myenteric plexus ganglia were used to examine the ability of NGF to stimulate morphological development in enteric neurons. NGF, in the presence of a serum-free medium, produced dose-dependent increases in neurite density, significant at 1 ng/ml and maximal at 100 ng/ml (4.5-fold increase vs. control). Maximum neurite length was also significantly increased at 1 ng/ml, with maximal effects at 100 ng/ml. Coincubation of NGF (50 ng/ml) with monoclonal NGF antibodies abolished increases in both neurite density (128 +/- 19 processes/mm for control, 369 +/- 19 for NGF, 183 +/- 28 for NGF+monoclonal antibodies) and neurite length. Exposure of enteric neurons to low concentrations of NGF (1 ng/ml) was also associated with increased mRNA levels for cytoskeletal genes. alpha-Tubulin mRNA levels were increased 3.9 +/- 0.7 times basal at 48 h. mRNA levels for microtubule-associated protein 2 were increased threefold at 48 h of NGF incubation. NGF demonstrates activities in cultured enteric ganglia that stimulate morphological development.

Inhibition of rat pancreatic exocrine secretion by neuropeptide Y: studies in vivo and in vitro

Neuropeptide Y (NPY) is a unique 36 amino acid peptide with strong sequence homology to pancreatic polypeptide and peptide YY. In the rat pancreas, NPY-positive fibers have been demonstrated in close association with exocrine structures, suggesting a regulatory role for the peptide. In conscious rats with pancreatic ductal cannulas, amylase output stimulated by cholecystokinin octapeptide (CCK-8: 0.2 microgram kg - 1 h -1) was dose-dependently inhibited by intravenous NPY infusion (20, 40, and 80 micrograms kg-1 h-1). Inhibitory effects were rapid in onset but reversed with cessation of NPY infusion. With continuous NPY infusion (40 microgram kg-1 h-1), prolonged inhibition of amylase output by the vagal stimulant 2-deoxyglucose (100 mg kg-1) was observed (greater than 50% inhibition in each of none consecutive 10-min periods). In contrast, NPY infusion in doses of 20, 40, or 80 micrograms kg-1 h-1 produced no alteration in immunoreactive somatostatin levels. In vitro, NPY incubation (10(-13)-10(-8) M) produced no change in basal amylase release from dispersed, purified acinar cells. In addition, co-incubation of NPY (10(-8)-10(-6) M) with CCK-8 (10(-13)-10(-8) M) produced no inhibition of CCK-stimulated amylase release from dispersed acini. In contrast, NPY (10(-6) M) produced significant inhibition of amylase release from pancreatic lobules that had been stimulated by 75 mM potassium (135 +/- 11% versus 177 +/- 18% of basal level) or by 25 microM veratridine (196 +/- 19% versus 398 +/- 152%).(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine content in rat brain is elevated by status epilepticus induced by lithium and pilocarpine

The effects of status epilepticus on the concentration, synthesis, release, and subcellular localization of acetylcholine, the concentration of choline, and the activity of acetylcholinesterase in rat brain regions were studied. Generalized convulsive status epilepticus was induced by the administration of pilocarpine to lithium-treated rats. The concentration of acetylcholine in the cortex, hippocampus, and striatum decreased prior to the onset of spike activity or status epilepticus. Once status epilepticus began, the concentration of acetylcholine increased over time in the cortex and hippocampus, reaching peak levels that were 461% and 304% of control levels, respectively, after 2 h of seizures. Such high in vivo levels of acetylcholine had not been reported previously following any treatment. During status epilepticus, the concentration of acetylcholine in the striatum returned to control levels after the initial depression, but did not accumulate to high levels as it did in the other two regions. The in vivo cortical efflux of acetylcholine was also increased during the seizures. Choline levels were increased by status epilepticus in all three brain regions. Inhibition of seizures by pretreatment with atropine blocked the increases of acetylcholine and choline. Synaptosomes prepared from the cortex and from the hippocampus of rats with status epilepticus had elevated concentrations of acetylcholine: in the hippocampus the acetylcholine was principally in the cytoplasmic fraction, whereas in the cortex the acetylcholine was elevated in both the cytoplasmic and the vesicular fractions. The extra acetylcholine was in a releasable compartment, since increased K+ in the media or ouabain increased the release of acetylcholine from cortical slices to a greater extent in tissue from seized rats than from controls.(ABSTRACT TRUNCATED AT 250 WORDS)