No abstract

The quality of nascent protein folding in vivo is influenced by the microdynamics of the proteins. Excessive collisions between proteins may lead to terminal misfolding, and the frequency of protein interactions with molecular chaperones determines their folding rates. However, it is unclear how immature protein dynamics are regulated. In this study, we analyzed the diffusion of immature tyrosinase in the endoplasmic reticulum (ER) of non-pigmented cells by taking advantage of the thermal sensitivity of the tyrosinase. The diffusion of tyrosinase tagged with yellow fluorescence protein (YFP) in living cells was directly measured using fluorescent correlation spectroscopy. The diffusion of folded tyrosinase in the ER of cells treated with brefeldin A, as measured by fluorescent correlation spectroscopy, was critically affected by the expression level of tyrosinase-YFP. Under defined conditions in which random diffusional motion of folded protein was allowed, we found that the millisecond-order diffusion rate observed for folded tyrosinase almost disappeared for the misfolded molecules synthesized at a nonpermissive high temperature. This was not because of enhanced aggregation at the high temperature, as terminally misfolded tyrosinase synthesized in the absence of calnexin interactions showed comparable, albeit slightly slower, diffusion. Yet, the thermally misfolded tyrosinase was not immobilized when measured by fluorescence recovery after photobleaching. In contrast, terminally misfolded tyrosinase synthesized in cells in which ␣-glucosidases were inhibited showed extensive immobilization. Hence, we suggest that the ER represses random fluctuations of immature tyrosinase molecules while preventing their immobilization.The maturation of proteins in the secretory pathway requires various sequential reactions including suppression of backward movements through the translocational channel by BiP (1); cleavage of the signal sequence and attachment of N-linked oligosaccharides (2); the prevention of nonproductive folding intermediates by various molecular chaperones (3); disulfide shuffling by disulfide isomerases possessing chaperone activity (4, 5); and proline isomerization (6). When these processes are not completed, proteins are disposed eventually. Recent extensive studies have been revealing the underlying molecular mechanisms of this destruction (7-11). However, there are also misfolded proteins that are able to maintain reversible folding for several hours after synthesis but somehow fail to exit the ER.1 A temperature-sensitive ts045 variant of the vesicular stomatitis virus glycoprotein (VSVG) is the best known example (12-14). It was thought that the defect in the exit of this glycoprotein from the ER and its transport to the Golgi could be explained by (a) uncompleted interactions of cargo proteins with the "ER matrix," which is composed of various chaperones and folding enzymes (15, 16) or (b) misfolded aggregates (13) that are too large to enter the COPIIcoated ER exit sites. However, measurements of...

Idiopathic acquired generalized anhidrosis is a very rare disease of unknown pathogenesis. We report a 25-year-old man with acquired generalized anhidrosis due to occlusion of the coiled ducts. He did not have sweat secretion over the entire surface of the body, including the palms and soles. Sweat-inducing stimuli provoked tingling pain on the skin. Pilocarpine iontophoresis on the forearm did not induce sweat secretion. Neurological examination did not reveal any abnormality in the central or peripheral nervous system. Skin biopsy showed that the coiled ducts were occluded by an amorphous eosinophilic substance. This amorphous eosinophilic substance was positive with periodic acid-Schiff (PAS) staining and was resistant to digestion by diastase. Electron microscopy demonstrated that the coiled ducts were completely occluded by an amorphous substance. The substance occluding the coiled ducts contained fibrous structures. These findings suggested that the acquired generalized anhidrosis in this patient was caused by occlusion of the coiled ducts by a PASpositive substance probably derived from dark cell granules.

A 50-year-old Japanese male visited our clinic in April 1999 with a 2-year history of self-healing, reddish papules on his right palm. On examination, there were grouped erythematous papules, 2–4 mm in size, which formed a relatively well-circumscribed erythematous plaque. A biopsy specimen showed a wedge-shaped, dense dermal infiltrate consisting of variously sized mononuclear lymphoid cells mixed with few large CD30-positive cells and inflammatory cells, suggesting the diagnosis of regional lymphomatoid papulosis (LyP). Analysis of the T cell receptor gene revealed a polyclonal pattern on lesional skin. Only 5 cases of LyP presenting in a regional distribution have been reported previously. Although the etiology of localized LyP remains unknown, considering that 2 of 5 reported patients developed widespread lesions regional LyP may be the initial presentation of typical LyP.