The articular cartilage consists of resident chondrocytes embedded within the extracellular matrix which contains several components such as collagen and hyaluronic acids (HA). CD44 is a major cell surface receptor for HA and is homologous to cartilage-link proteins. Although CD44 is present in cartilage, it is not clear if chondrocytes adhere to HA through CD44 or whether such adhesion changes the function of chondrocytes. We studied the molecular mechanisms of CD44-related chondrocyte adhesion to HA and the effects of such adhesion on chondrocyte function. Experiments were performed using the human chondrosarcoma-

The concept of differential regulation of certain adhesion molecules on different cell subsets and their relevance to cell functions has emerged in recent years. The initial event in bone remodeling is an increase in osteoclastic bone resorption and cell adhesion between osteoclastic precursors and bone marrow stromal cells or osteoblasts is known to commit the osteoclast development. Here, we show that human osteoblasts can be divided into two subsets based on the expression of the intercellular adhesion molecule (

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Golgi a-mannosidase II (a-Mll) is an enzyme involved in the processing of N-linked glycans. Using a previously isolated murine cDNA clone as a probe, we have isolated cDNA clones encompassing the human a-MII cDNA open reading frame and initiated isolation of human genomic clones. During the isolation of genomic clones, genes related to that encoding a-MIl were isolated. One such gene was found to encode an isozyme, designated acMIIx. A 5-kb cDNA clone encoding a-MIIX was then isolated from a human melanoma cDNA library. However, comparison between a-MIIX and a-MIl cDNAs suggested that the cloned cDNA encodes a truncated polypeptide with 796 amino acid residues, while a-MI consists of 1144 amino acid residues. To reevaluate the sequence of a-MIIx cDNA, polymerase chain reaction (PCR) was-performed with lymphocyte mRNAs. Comparison of the sequence of PCR products with the a-MIIX genomic sequence revealed that alternative splicing of the a-MIIX transcript can result in an additional transcript encoding a 1139-amino acid polypeptide. Northern analysis showed transcription of a-MIIX in various tissues, suggesting that the a-MIIX gene is a housekeeping gene. COS cells transfected with c-MIIX cDNA containing the full-length open reading frame showed an increase of a-mannosidase activity. The ca-MIIX gene was mapped to human chromosome 15q25, whereas the a-MIl gene was mapped to 5q21-22.a-Mannosidase (a-M) activities are involved in both biosynthesis and catabolism of N-linked glycans (1, 2). These enzyme activities are present in cells ranging from yeast to human. There are different forms of a-Ms: lysosomal a-Ms are soluble and involved in degradation of N-glycans, endoplasmic reticulum (ER) and Golgi a-Ms are involved in processing of newly synthesized N-glycans, and cytoplasmic a-Ms may be involved in degradation of dolichol intermediates that are not needed for protein glycosylation or oligosaccharides derived from glycoprotein turnover in the ER (1).. Substrate specificities of these a-Ms differ from each other, and Golgi a-MIl specifically hydrolyzes two peripheral mannosyl residues from Manal1-6(Manal --3)Manal ->6(GlcNAcf31--2Mana1 ->3)[Man/31 ->4GlcNAc,lB --4GlcNAc31 ->]asparagine structure. Several a-Ms have been cloned to date. These include Golgi a-MIT (3, 4), ER/cytosolic a-MI (5), two isozymes of Golgi a-MI (6-8), lysosomal a-M (9), Dictyostelium a-M (10), and yeast a-M (11) The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.