Abstract-There is evidence that telomeres, the ends of chromosomes, serve as clocks that pace cellular aging in vitro and in vivo. In industrialized nations, pulse pressure rises with age, and it might serve as a phenotype of biological aging of the vasculature. We therefore conducted a twin study to investigate the relation between telomere length in white blood cells and pulse pressure while simultaneously assessing the role of genetic factors in determining telomere length. We measured by Southern blot analysis the mean length of the terminal restriction fragments (TRF) in white blood cells of 49 twin pairs from the Danish Twin Register and assessed the relations of blood pressure parameters with TRF. TRF length showed an inverse relation with pulse pressure. Both TRF length and pulse pressure were highly familial. We conclude that telomere length, which is under genetic control, might play a role in mechanisms that regulate pulse pressure, including vascular aging. This process also occurs in vivo because an inverse relation exists between telomere length in replicating somatic cells and the age of human beings who have donated these cells (References 5 through 9; reviewed in References 1 through 4). Thus, the replicative history of somatic cells is a major determinant of telomere length. Another determinant of telomere length is heredity, since the high variability in this parameter among human beings is to a large extent genetically determined. 5 Recent experimental data support the concept that telomeres might serve as "biological clocks," pacing not only life span at the cellular level but also aging at the systemic level. These data show that (1) the prevention of telomere attrition by the forced expression in cultured somatic cells of the catalytic component of telomerase, the reverse transcriptase that adds telomere repeats onto the ends of chromosomes, postpones replicative senescence 10,11 and (2) the "knockout" of telomerase in the mouse amplifies some characteristics associated with systemic aging in later generations of mice that exhibit substantially shortened telomere length. 12 At least 2 fundamental questions therefore arise with respect to the clinical implications of telomere biology. First, can the length of telomeres serve as an in vivo indicator of biological aging of replicating somatic cells in different organ systems of humans? A related question is: Is the aging of tissues from persons who are genetically endowed with long telomeres likely to occur later in life or at a slower pace than of tissues from persons who inherit short telomeres? Second, which biological parameters can serve as indicators of aging in human beings, since for obvious reasons chronological age (which is determined by calendar time) is a poor criterion for biological aging?In light of these considerations, this work had 2 goals. The first goal was driven by the following concept. Since in industrialized nations pulse pressure increases with age, 13 pulse pressure might serve as a phenotype of cardiovascular agin...

By using the large cytoplasmic domain of the nicotinic acetylcholine receptor (AChR) ␣4 subunit as a bait in the yeast two-hybrid system, we isolated the first cytosolic protein, 14-3-3, known to interact directly with neuronal AChRs. 14-3-3 is a member of a family of proteins that function as regulatory or chaperone/ scaffolding/adaptor proteins. 14-3-3 interacted with the recombinant ␣4 subunit alone in tsA 201 cells following activation of cAMP-dependent protein kinase by forskolin. The interaction of 14-3-3 with recombinant ␣4 subunits was abolished when serine 441 of the ␣4 subunit was mutated to alanine (␣4 S441A ). The surface levels of recombinant wild-type ␣4␤2 AChRs were ϳ2-fold higher than those of mutant ␣4 S441A ␤2 AChRs. The interaction significantly increased the steady state levels of the ␣4 subunit and ␣4␤2 AChRs but not that of the mutant ␣4 S441A subunit or mutant ␣4 S441A ␤2 AChRs. The EC 50 values for activation by acetylcholine were not significantly different for ␣4␤2 AChRs and ␣4 S441A ␤2 AChRs coexpressed with 14-3-3 in oocytes following treatment with forskolin. 14-3-3 coimmunopurified with native ␣4 AChRs from brain. These results support a role for 14-3-3 in dynamically regulating the expression levels of ␣4␤2 AChRs through its interaction with the ␣4 subunit. Neuronal nicotinic acetylcholine receptors (AChR)1 are a family of ligand-gated, cation-selective, homo-or heteropentameric ion channels expressed in the peripheral and central nervous system (1, 2). A multitude of neuronal AChR subtypes assembled from different combinations of ␣2-␣9 and ␤2-␤4 subunits have been identified (3,4 (7), and show attenuated self-administration of nicotine (8) suggesting that ␣4␤2 AChRs have a role in mediating addiction to nicotine. The normal and pathophysiological functions mediated by ␣4␤2 AChRs are of significant importance to human health. Some inherited forms of epilepsy, such as the autosomal dominant nocturnal frontal lobe epilepsies, are caused by ␣4␤2 AChRs harboring at least two separate mutations within their ␣4 subunit (9 -12). Most recently, ␣4␤2 AChRs, among other ␤2 subunit-containing AChRs, have been implicated in neuronal survival during aging, as surmised from the neurodegeneration observed in ␤2-subunit knock-out mice (13).The ␣4 subunit, like the other AChR subunits, consists of an extracellular N-terminal domain, followed by three transmembrane domains (M1-M3), a large cytoplasmic domain, a fourth transmembrane domain (M4), and a short extracellular C terminus. The large cytoplasmic domain is highly divergent among the various subunits, and this sequence divergence presumably provides the diversity necessary for different AChR subtypes to interact directly with cytosolic proteins of different function. To identify such proteins associated with ␣4␤2 AChRs, we used the large cytoplasmic domain of the ␣4 subunit as a bait to screen a mouse brain cDNA yeast two-hybrid library. Here we describe the isolation of a known protein termed 14-3-3. The 14-3-3 proteins family consists of sev...

IDDM is a polygenic and autoimmune disorder in which subsets of white blood cells (WBCs) are engaged in the destruction of beta-cells of the pancreas. The mechanisms that account for the abnormal behavior of these cells in IDDM are not fully understood. By measuring the mean length of telomeres of WBCs from patients with IDDM, we tested the concept that telomeres might play a role in IDDM. We examined the lengths of the terminal restriction fragments (TRFs) of DNA of WBCs from 234 white men comprising 54 patients with IDDM, 74 patients with NIDDM, and 106 control subjects. When adjusted for age, the TRF length from WBCs of patients with IDDM was significantly shorter than that of nondiabetic control subjects (mean +/- SE: 8.6 +/- 0.1 vs. 9.2 +/- 0.1, P = 0.002). No significant difference was observed between the TRF length from WBCs of patients with NIDDM versus nondiabetic subjects. Neither the duration nor the complications of IDDM (i.e., nephropathy and hypertension) had an effect on the TRF length of WBCs from patients with IDDM. The shortened TRF length of WBCs of patients with IDDM likely reflects a marked reduction in the TRF length of subsets of WBCs that play a role in the pathogenesis of IDDM.