November 28
PROGRAM

04

Glycoscience : diversity and integration

Regulation of hyaluronan synthesis
and its importance fortissue remodeling and cancer
Markku I. Tammi, M.D., Ph.D.
Professor, Institute of Biomedicine,
School of Medicine, University of Eastern Finland, FINLAND

Markku I. Tammi
ProfileMarkku Tammi is a cell biologist who has
worked on proteoglycans, lately on hyaluronan and its involvement in disease. He
obtained M.D. in the University of Turku
in 1975, followed by Ph.D. in 1979 with athesis entitled “Arterial Glycosaminoglycans in Atherogenesis”. After dissertation,until 1994, he worked with Prof. Heikki
Helminen in the University of Kuopio on
proteoglycans of articular cartilage, especially their response to joint loading. During 1984-1986 he made a postdoctoral fellowship in the University of California in
Berkeley, studying yeast glycoproteins withProf. Clinton Ballou. In 1994-1996 hejoined, together with his wife Raija Tammi,M.D. Ph.D, Dr. Vincent Hascall’s laboratory in Lerner Research Institute, Cleveland,to establish a new organotypic model for
research on hyaluronan metabolism andfunctions in skin epidermis. After returning to Kuopio, the work was continued toshow that hyaluronan as a major epidermal
matrix molecule is strongly involved in keratinocyte migration, proliferation and differentiation, and epidermal wound healing. During the last 15 years, collaboratingwith local clinicians, they have also demonstrated that hyaluronan accumulates incertain cancers and forms a strong risk factor for unfavourable prognosis. Currently,
his major interest is in the regulation of
hyaluronan synthesis, both at transcriptional and posttranslational levels, andpossibilities to use this information for diagnostic and therapeutic use. The work has
resulted in a discovery of the key role ofcellular UDP-GlcNAc concentration as a
substrate for hyaluronan synthesis, and asa regulator of hyaluronan synthase transcription, and a modifier of HAS enzyme
activity, the latter two via cytosolic protein
O-GlcNAc modifications.

Hyaluronan is a multimillion molecularmass, linear, non-sulfated glycosaminoglycan with a repeating structure of[β1->3GlcNAc -β1->4GlcUA]. It is not
attached to a core protein, but is synthesized as a free chain that runs out of thecell through a pore in plasma membrane,
the pore formed by hyaluronan synthases(HAS1-3), the transferases that constructthis polysaccharide using cytosolic UDPsugars as substrates 1). This unique way ofsecretion results in a cell surface glycocalyx, several micrometers thick 2)3), andeventual release of hyaluronan into extracellular space where it organizes the matrix
by aggregating with specific proteoglycans
and forming transient cross-links withother matrix proteins.
Besides a lubricant and space filler between
the cells and fibrous matrix components,
hyaluronan has been recognized as animportant signaling molecule, governing
processes like cell migration, proliferation,inflammation, and malignant growth. In
general, whenever tissues undergo remodeling, whether it be embyonic development, wound healing, or cancer, hyaluronan synthesis is activated. Expression of
the three Has genes are subject to regulation by multiple stimuli, like growth factors, cytokines, prostaglandings, and hormones 1).
As the only Has with its deletion embryonically lethal, Has2 regulation has received
most interest. Has2 promoter contains
several response elements accounting forthe influences of the inflammatory andgrowth promoting effectors mentioned
above 1). In addition, Has2 expression isstrongly modulated by the metabolic stateof the cell, mediated by AMPK activity andcellular glucose supply, the latter throughhyaluronan, glucose,
Keywords UDP-GlcNAc,
O -GlcNAc transferase, cancer

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the 20th Anniversary of the Mizutani Foundation for Glycoscience

UDP-GlcNAc content and consequent
O-GlcNAc-signaling (Figure 1) 4)5).
Besides influencing Has2 gene expression 5),
UDP-GlcNAc content and O-GlcNAcsignaling have also more direct effects on
HAS2 activity and hyaluronan synthesis.
As a HAS substrate UDP-GlcNAc caneither stimulate or inhibit hyaluronan
synthesis, according to its cellular content 4). In addition, HAS2 itself contains
O-GlcNAc-moieties, which increase thestability or enzymatic activity of HAS protein (Fig.1). Furthermore, especially UDPGlc secreted or leaked from cells stimulate
Has2 expression by activating a G-protein
coupled UDP-sugar receptor. Thus, glucose and its UDP-sugar metabolites arestrongly involved in the regulation of hyaluronan synthesis at multiple levels.
We have shown that hyaluronan accumulation in malignant tumors like breast,
prostate, gastric, colon and ovarian cancers is an unfavourable prognostic factor
for patient survival 6). Immunohistochemical and real-time RT-PCR analyses of the
HAS enzymes done in breast, ovarian andendometrial cancers have not revealed
unequivocal correlation with hyaluronan
content, suggesting that mechanisms otherthan gene expression are also involved. We
are currently exploring the possibility thatthe aerobic glycolysis typical for cancer
cells (Warburg effect), associated with highglucose uptake, contributes to the hyaluronan deposits via enhanced UDP-sugar
supply. Hyaluronan and its synthesis arerecognized as novel targets of therapy incancer, but perhaps also in other chronic,
low intensity inflammatory processes inwhich hyaluronan synthesis is increased,
metabolic syndrome and arterial diseases
as examples.

Figure 1. Multiple roles of UDP-GlcNAc in hyaluronan synthesis.
1. As a substrate of HAS enzymes UDP-GlcNAc concentration has a direct influence on the rate of hyaluronan synthesis.
2. With UDP-GlcNAc abundance, HAS serine/threonine residues are subject to modification by O-GlcNAc, mediated by OGT and resulting
in enhanced enzymatic activity of HAS.
3. The cellular content of UDP-GlcNAc influences the level O-GlcNAc modifications in the transcription factors SP1 and YY1, which inturn control Has2 gene expression. The cellular content of UDP-GlcNAc is increased by feeding cells with glucose or even more withglucosamine, and decreased by mannose. UDP-GlcNAc is synthesized in cytosol, where it is used for hyaluronan synthesis and O-GlcNAc
modifications by OGT. Golgi membrane transporters are expected to maintain a high levels of UDP-sugars in this compartment despite
concentration fluctuations in the cytosol.

References1) 	Tammi RH, Passi AG, Rilla K, Karousou E, Vigetti D, Makkonen K, Tammi
MI. Transcriptional and posttranslational regulation of hyaluronan synthesis. FEBS J. (278): 1419-1428, 2011.
2) 	Kultti A, Rilla K, Tiihonen R, Spicer AP, Tammi RH, Tammi MI. Hyaluronan synthesis induces microvillus-like cell surface protrusions. J Biol Chem(281):15821-15828, 2006.
3) 	Rilla K, Kultti A, Tammi M, Tammi R. Pericellular hyaluronan coat visualized in live cells with a fluorescent probe is scaffolded by plasma membrane
protrusions. J Histochem Cytochem (56): 901-910, 2008.
4) 	Jokela TA, Jauhiainen M, Auriola S, Kauhanen M, Tiihonen R, Tammi MI,Tammi RH. Mannose inhibits hyaluronan synthesis by downregulation of

the cellular pool of UDP-N-Acetylhexosamines. J. Biol. Chem. (283):76667673, 2008.
5) 	Jokela TA, Makkonen KM, Oikari S, Kärnä R, Koli E, Hart GW, Tammi RH,Carlberg C, Tammi MI. Cellular content of UDP-N-Acetylhexosamines
controls hyaluronan synthase 2 expression and correlates with O-GlcNAc
modification of transcription factors YY1 and SP1. J Biol Chem (286): 3363233640, 2011.
6) 	Tammi R, Kultti A, Kosma V-M, Pirinen R, Auvinen P, Tammi M. Hyaluronan in human tumors: Pathobiological and prognostic messages from cellassociated and stromal hyaluronan. Semin Cancer Biol (18): 288-295, 2008.

Commemorative Symposium

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