Conventional kinesin Holoenzymes are composed of heavy and light chain homodimers
BIOCHEMISTRY
Authors: DeBoer, Scott R.; You, YiMei; Szodorai, Anita; Kaminska, Agnieszka; Pigino, Gustavo; Nwabuisi, Evelyn; Wang, Bin; Estrada-Hernandez, Tatiana; Kins, Stefan; Brady, Scott T.; Morfini, Gerardo
Abstract
Conventional kinesin is a major microtubule-based motor protein responsible for anterograde transport of various membrane-bounded organelles (MBO) along axons. Structurally, this molecular motor protein is a tetrameric complex composed of two heavy (kinesin-1) chains and two light chain (KLC) subunits. The products of three kinesin-1 (kinesin-1A, -1B, and -1C, formerly KIF5A, -B, and -C) and two KLC (KLC 1, KLC2) genes are expressed in mammalian nervous tissue, but the functional significance of this subunit heterogeneity remains unknown. In this work, we examine all possible combinations among conventional kinesin subunits in brain tissue. In sharp contrast with previous reports, immunoprecipitation experiments here demonstrate that conventional kinesin holoenzymes are formed of kinesin-1 homodimers. Similar experiments confirmed previous findings of KLC homodimerization. Additionally, no specificity was found in the interaction between kinesin-1s and KLCs, suggesting the existence of six variant forms of conventional kinesin, as defined by their gene product composition. Subcellular fractionation studies indicate that such variants associate with biochemically different MBOs and further suggest a role of kinesin-1s in the targeting of conventional kinesin holoenzymes to specific MBO cargoes. Taken together, our data address the combination of subunits that characterize endogenous conventional kinesin. Findings on the composition and subunit organization of conventional kinesin as described here provide a molecular basis for the regulation of axonal transport and delivery of selected MBOs to discrete subeellular locations.
Comprehensive assessment of rheumatoid arthritis susceptibility loci in a large psoriatic arthritis cohort
ANNALS OF THE RHEUMATIC DISEASES
Authors: Bowes, John; Ho, Pauline; Flynn, Edward; Ali, Faisal; Marzo-Ortega, Helena; Coates, Laura C.; Warren, Richard B.; McManus, Ross; Ryan, Anthony W.; Kane, David; Korendowych, Eleanor; McHugh, Neil; FitzGerald, Oliver; Packham, Jonathon; Morgan, Ann W.; Bruce, Ian N.; Barton, Anne
Abstract
Objective A number of rheumatoid arthritis (RA) susceptibility genes have been identified in recent years. Given the overlap in phenotypic expression of synovial joint inflammation between RA and psoriatic arthritis (PsA), the authors explored whether RA susceptibility genes are also associated with PsA. Methods 56 single nucleotide polymorphisms (SNPs) mapping to 41 genes previously reported as RA susceptibility loci were selected for investigation. PsA was defined as an inflammatory arthritis associated with psoriasis and subjects were recruited from the UK and Ireland. Genotyping was performed using the Sequenom MassArray platform and frequencies compared with data derived from large UK control collections. Results Significant evidence for association with susceptibility to PsA was found to a SNP mapping to the REL (rs13017599, p(trend)=5.2x10(4)) gene, while nominal evidence for association (p(trend)<0.05) was found to seven other loci including PLCL2 (rs4535211, p=1.7x10(-3)); STAT4 (rs10181656, p=3.0x10(-3)) and the AFF3, CD28, CCL21, IL2 and KIF5A loci. Interestingly, three SNPs demonstrated opposite effects to those reported for RA. Conclusions The REL gene, a key modulator of the NF kappa B pathway, is associated with PsA but the allele conferring risk to RA is protective in PsA suggesting that there are fundamental differences in the aetiological mechanisms underlying these two types of inflammatory arthritis.