While a variety of cultural, psychological and physiological factors contribute to variability in both clinical and experimental contexts, the role of genetic factors in human pain sensitivity is increasingly recognized as an important element. This study was performed to evaluate genetic influences on variability in human pain sensitivity associated with gender, ethnicity and temperament. Pain sensitivity in response to experimental painful thermal and cold stimuli was measured with visual analogue scale ratings and temperament dimensions of personality were evaluated. Loci in the vanilloid receptor subtype 1 gene (TRPV1), delta opioid receptor subtype 1 gene (OPRD1) and catechol O-methyltransferase gene (COMT) were genotyped using 5' nuclease assays. A total of 500 normal participants (306 females and 194 males) were evaluated. The sample composition was 62.0% European American, 17.4% African American, 9.0% Asian American, and 8.6% Hispanic, and 3.0% individuals with mixed racial parentage. Female European Americans with the TRPV1 Val(585) Val allele and males with low harm avoidance showed longer cold withdrawal times based on the classification and regression tree (CART) analysis. CART identified gender, an OPRD1 polymorphism and temperament dimensions of personality as the primary determinants of heat pain sensitivity at 49 degrees C. Our observations demonstrate that gender, ethnicity and temperament contribute to individual variation in thermal and cold pain sensitivity by interactions with TRPV1 and OPRD1 single nucleotide polymorphisms.

Endocytic trafficking plays an important role in the regulation of the epidermal growth factor receptor (EGFR). To address if cellular kinases regulate EGFR internalization, we used anisomycin, a potent activator of kinase cascades in mammalian cells, especially the stress-activated mitogen-activated protein (MAP) kinase subtypes. Here, we report that activation of p38 MAP kinase by anisomycin is sufficient to induce internalization of EGFR. Anisomycin and EGF employ different mechanisms to promote EGFR endocytosis as anisomycininduced internalization does not require tyrosine kinase activity or ubiquitination of the receptor. In addition, anisomycin treatment did not result in delivery and degradation of EGFR at lysosomes. Incubation with a specific inhibitor of p38, or depletion of endogenous p38 by small interfering RNAs, abolished anisomycininduced internalization of EGFR while having no effect on transferrin endocytosis, indicating that the effect of p38 activation on EGFR endocytosis is specific. Interestingly, inhibition of p38 activation also abolished endocytosis of EGFR induced by UV radiation. Our results reveal a novel role for p38 in the regulation of EGFR endocytosis and suggest that stimulation of EGFR internalization by p38 might represent a general mechanism to prevent generation of proliferative or antiapoptotic signals under stress conditions.

In mammals, the mucolipin family includes three members mucolipin-1, mucolipin-2, and mucolipin-3 (MCOLN1-3). While mutations in MCOLN1 and MCOLN3 have been associated with mucolipidosis type IV and the varitint-waddler mouse phenotype, respectively, little is known about the function and cellular distribution of MCOLN2. Here we show that MCOLN2 traffics via the Arf6-associated pathway and colocalizes with major histocompatibility protein class I (MHCI) and glycosylphosphatidylinositol-anchored proteins (GPI-APs), such as CD59 in both vesicles and long tubular structures. Expression of a constitutive active Arf6 mutant, or activation of endogenous Arf6 by transfection with EFA6 or treatment with aluminum fluoride, caused accumulation of MCOLN2 in enlarged vacuoles that also contain MHCI and CD59. In addition, overexpression of MCOLN2 promoted efficient activation of Arf6 in vivo, thus suggesting that MCOLN2 may have a role in the traffic of cargo through the Arf6-associated pathway. In support of this we found that overexpression of a MCOLN2 inactive mutant decreases recycling of CD59 to the plasma membrane. Therefore, our results indicate that MCOLN2 localizes to the Arf6-regulated pathway and regulates sorting of GPI-APs.