0022- 202X/84/8304 -02G I $02.00/ 0 THE JO HNAL OF I NVESTJf:ATI VE DEHMATOJ.O(:Y, 83:26 J- 2fi·l, l984 Cop y righ l <c> 1984 by The Williams & Wilkin' Co.

Vol. 83, No. 4 Print.ed in U.S.A.

Calcium-Activated, Phospholipid-Dependent Protein Kinase in Pig Epidermis

HIROKO KOIZ UM I, M .D., KENJI ADACHI , M.D., PH .D ., MASATO TSUTSUI, M .D. , SATOSHI ITAMI , M.D.,

HIROSHI KATAYAMA, M.D., PH.D., AND KENNETH M. HALPRIN, M.D .

Veterans Administrat-ion. Medical Cenl"er, Miami, and Department of Dermatology, University of Miami School of Medidn.e, Miami, Florida, U.S.A.

We investigated calcium-activated, phospholipid-de­pendent protein kinase in pig epidermis. Pig epidermal homogenates were centrifuged at 30,000 g for 30 min, and the supernatant was applied on a DEAE-cellulose column for purification. The partially purified enzyme was stimulated by simultaneous addition of Ca2

+ and phospholipid. Successive addition of small amounts of diolein further activated the enzyme activity. The cal­cium-activated phospholipid-dependent protein kinase p referentially phosphorylated serine residues and its endogenous substrate protein in the pig epidermis has a molecular weight of about 97,000.

Calcium-activated, phospholipid-dependent protein kinase (protein kinase C) was originally described by T akai et al [1,2 ] . It was found in rat brain and subsequently in various t issues and phyla [3]. Protein kinase C requires the simulta­neous presence of Ca2

+ and phosphol ipid for catalytic activity, and small amounts of diacylglycerol increase t he affinity of the enzyme for CaH as well as for phospholipid [4- 6]. It has been suggested t hat protein kinase C plays an important role in releas ing serotonin from platelets [7,8]. It appears also to play a role in the process of different iation of certain types of cells [9 ], and recently protein kinase itself has been suggested to be t he receptor protein of t umor-promoting phorbol esters [10-12].

Epide rmis has active cell proliferation and differentiation. Hence, one can foresee that t his enzyme may have an important role in epidermal cell metabolism. In t he present communica­tion, we describe the presence of and the biochemical nature of protein kinase C in pig epidermis.

MATERIALS AND METHODS

Enzym e Preparation

Epi d e rmis was obtained from the backs of domestic pigs weighing 17-21 lb, with a Castroviejo kera tome adjusted to 0.2 mm. It was im mediately homogenized in a conical glass homogenizer at 4 OC with 5 volumes (w/v) of 20 mM Tris H Cl (pH 7.5) conta ining 0.25 M sucrose, 2 mM EDTA, and 10 mM ethyleneglycoltetraacetic ac id (EGTA). All followin g procedures were performed at 4 °C. The homogenate was centrifuged at 30,000g for 30 min. The supernatant was filtered through glass wool to remove lipids. The fil t rate was added on a diethylamino­ethyl (DEAE}-cellulose (DE52) column (1.6 X 10 em), which was

Ma nusc rip t received Februa ry 6, 1984; accepted for publication May

25, 1984. Th is work was supported by Nationa l Institutes of Health Grant

No. 17179 (N JAMDD) a nd the Dermato logy Foundation of Miami . Reprint requests to: Kenji Adachi , M.D., VA Medica l Center, 1201

N. W. 16th Street, Miami , Florida 33125 . Abbreviations:

DEAE: diethylaminoethyl EGTA: ethyleneglycoltetraacetic ac id protein kinase A: cA MP-dependent protein kinase protein kinase C: calcium -activa ted, phospholipid-dependent pro­

tein kinase SDS: sodium dodecyl sulfate TP A: 12-0-tetradecanoylphorbol-13-acetate

261

previously equilibrated with 20 mM Tris-HCl at pH 7.5 conta ining 2 mM EDTA, 5 mM EGTA, and 50 mM 2-mercaptoethano l. After t he column was washed, t he enzyme was eluted with a linear gradient of NaCI (0- 0.4 M). The fractions contai ning t he enzyme activ ity were pooled, dialyzed with 20 mM Tris- HCl, pH 7.5, containing 0.5 mM EGTA and 50 mM 2-mercaptoetha nol, and concentrated to 2-3 ml using an Am icon concent rating system.

Protein J<in.ases Assay

Th~ condit ions used were simila r to those previously described [1] . Protem kmases were assayed by measuring the incorporation of 32p from [-y-"2P ]A!P into lys ine-rich histone (hi tone IIJ -S, Sigma). The standard reactiOn mixture contained in a fina l volume of 50 1-'1: 1 '"mol ~ris- HC I pH 7.5, 250 n~!'o l magnesium acetate, 10 1-'g of lysine-ri ch histone, 0.5 nmol of [-y- ·P]ATP (0.2-0.8 1-'Ci / nmol, Amersham) and the enzyme solu t ion to be ass~yed. For the p rote in kinase C assay 1 1-'g

of phospha tJdylsenne (S1gma ), 0.2 1-'g of diolein (Sigma), and 5 or 25 nmol of CaCh were added to t he reaction mixture. For the adenosine 3' ,5' -monophosphate-dependent protei n kinase (protein kinase A) as­say 50 pmol of cAMP was added to t he reaction mixture.

The reaction was started by addi t ion of ATP. After incubation for 10 min at 30°C, the reaction was stopped by t he addit ion of 20 1-'1 of glacia l acetic acid. Aliquots were spotted on a 2 X 2 em phosphocellu lose paper (Whatman P81) and washed for 75 min with several changes of double-diStilled wate r [1 3]. The papers were dried with acetone and counted in 10 ml of liqu irl sc in t illation solution (4 g of Omnifluor (New England Nuclear) and_ ~0 ml of Biosolv BBS-3 (Beck man)/ li ter of to luene ). The radwnctJv ity was counted wit h a Packard scintillation spectrometer.

The prote in conten t was determined by the method of Lowry et a l [14].

Phosphorylation of Pig Epidermal Protein. by Protein /(in.ase C

A supernatant fraction was obtained after cent rifugation (30 000 g

for 30 min) of t he epidermal homogenate as done for the crude e~tract of pig epidermal protein kinase C. Histone was omitted from the reaction mixture and t he supernatant was used as substrate for protein kinase C. The reaction was stopped by spotting t he a liquots on a 2 x 2 em piece of filter pape r (Whatman 3MM) and immediately immersing it into a la rge vo lume of 10% t ri chloroacetic acid (TCA) solu tion, which was changed t wice. T he filter papers were rinsed wi t h acetone and their radioactivi t ies counted as described previously. Alternatively t he reac­t ion was stopped by adding 2 volumes of 10% TCA into the reaction mixture. After 1 h standing at room tempera ture, acid-precipitable radioactivity was counted. For electrophoresis t he reaction was stopped by adding the stopping solu tion consisting of a fin a l concentration of 0.0625 M Tris-H CI pH 6.8, 2% sodium dodecyl sulfate (SDS), 5% 2-mercaptoethanol, 10% glycerol. The mixture was boiled for 3 min and an a liquot was subjected to SDS-polyacrylamide gel electrophoresis as described by Laemmli [15]. After t he electrophoresis, t he gel was stained with Coomassie Bri lliant Blue R25. The dried ge l was subjected to auto radiography with Kodak x- ray film .

RESULTS

Partial Purification of Protein Kinase C

The crude extract was applied to the DE52 column and the column was eluted as shown in Fig 1. When each fraction was

• Sigma Cata logue #P-664 1 with 98-99% purity when prepared a l­ways yields satisfactory results. It is used within 3-4 months of shipment.

262 KOIZ UMI ET AL

::::1.

0 ~

c .E 0 ~

;:;--0 X

E Q._ u

2

F1 r. 1. DE52 column chromatography or protein kinase from pig epidermis. The crude extract was applied to a DE52 column (1.6 x 10 em) and equilibrated with 20 mM Tris- HCI bu ffer at pH 7.5 containing 2 mM EDTA, 5 mM EGTA, and 50 mM 2- mercaptoethanol. After the column was washed with 100 ml of the same buffer, protein kinases were elu ted by a 250-ml linear concentration gradient of NaCI in the sa me buffer. Fractions of 3 ml each were coll ected. Enzyme activity was assayed using a 1 0-,.d aliquot of each fraction. Protein kinase activities with the standard reaction mixture described in the experi­mental procedure were shown as (0-0), those with the reaction assay mixture containing 500 I'M CaCI2, ll'g phosp hatidylserine, and 200 ng diolein (e- e) , and those with the basic reaction mixture plus 1 J.1M cA MP (6-6) .

assayed without phosphatidylserine, diolein, or cAMP, no en­zyme act ivity was detected. When 500 J.LM of CaClz was added to the standard assay mi xture, again no enzyme activity was found (data not show n). Only when phosp hatidylse rine , diolein , and CaCl2 were added together to t he assay mixtu re, could the protein kinase activities be measured . The elution pattern shows two peaks; the first peak was a lways higher than t he second peak a nd sometimes the second peak could not be found.

With t he addition of 1 J.LM cAMP, two pea ks of protein kinase A were show n. The first peak appears at a lower NaCl concen­tration t ha n that of the major peak of protein kinase C, and t he seco nd peak at higher NaC l concentration t han that of the seco nd pea k of protein kinase C. The first peak of protein kinase A shows cAMP-dependent protein kinase type l isozyme, the second type ll isozyme. If t he t issue was homogenized vigorously, t he peak of type I isozyme disappeared. This obser­vation is cons is tent with our previous work (16). In t his partic­ula r experiment in F ig 1, t he homogenization was moderate so t hat the peak of type I isozyme was small but could be detected . This phenomenon is due to t he dissociation of type I isozyme into its subunits . Therefore, in subsequent experiments, we homogenized t he t issue vigorously to remove the peak of type I isozyme a nd used the major peak of protein kinase C as t he enzyme source. Fig 2 s hows t he time course of t he phosphoryl­ation reaction of protein kinase C with lysine- rich histone as substrate. The enzymatic activi ty increased linea rly for 10 min a nd then gradually reac hed a p lateau. In the subsequen t exper­iments, we chose a 10-min incubation period.

Fig 3 shows t he activation of protein kinase C by phospha ­t idylserine. In the presence of 1 mM EGTA the protein kinase C was not stimulated by phosphatidylse rine or diolein . With t he addition of 100 J.LM CaCl2 , t he enzyme was stimulated linea rly with t he increased concent rations of phosphatidylser­ine; on t he other hand, it was not clea rly activated by diolein

--... (!)

6

5

Vol. 83, No. 4

~ ~ E ?

0 2 E

.f6 .f6

c

1 /,

•t / t.

•I -------0 # 0 ----0 ~'I o-o- o- o- o----

0 6-if I I I 0 10 20

INCUBATION TIME (min)

I 30

FIG 2. Time course of phosphorylation of lys ine-rich histone by prote in kinase C. Protein kinase C activity was assayed with (e -e) or without (0-0) phosphatidylserine, diolein, and CaCI2 • The net protein kinase C activi ties and the difference between these assays are shown (6- 6) .

2.0

c 1.5 ·a:; +-' 0

Q: en E .___ c .E 1.o .___ Q)

0 E c

~· •

0

0

0.5 //0

• 0

II • .n • II ;;-~·!-: __ :-----o----------0 "" I I

0 0.5 __ PS (1Jg) _1 .0_ 0 100 Diolein (ng) 200

FIG 3. Effects of various concentrations of phosphat idylserine and diolein on the activation of protein kinase C. The protein kinase C activities were assayed under the standard condition with various amou nts of phosphatidylserine and diolein . In the presence of EGTA (l mM) to chelate Ca2

+ (100 J.1M) , practically no or li ttle enzyme activity is detected in the reaction mixture containing phosphatidylserine (6-6), or both phosphatidylserine and diolein (•- •l . In the presence of Ca2

+ (100 J.1M), t he phosphatidylserine-dependent activation is dem­onstrated (0 - 0 ). In the presence of Ca2+, diolein at various concen­trations did not clearly activate the enzyme (data not shown). However, the simultaneous addition of phosphatidylserine and diolein alwa,·s show synergistic effects, as shown (e- e). ·

Oct. 1984 CALCIUM-ACTIVATED PHOSPHOLIPID-DEPENDENT PROTEIN KINASE 263

at the concentration range tested. In the presence of CaH, however, the simultaneous addition of diolein and phosphati­dylserine caused the synergistic and maximum stimulation of the protein kinase C activit ies (Fig 3) .

Fig 4 shows the dependency of protein kinase C on calcium for the phosphorylation of the lysine-rich histone as the sub­strate. Maximal activation occurred with 0.1-0.5 mM of Ca2+

in the presence of phosphatidylserine. Diolein could not acti ­vate the enzyme without phosphatidylserine.

Table I summarizes the effect of various activators of protein kinase C. In the presence of both 100 11M CaCb and freshly sonicated (1 J.Lg) phosphatidylserine, 12-0-tetradecanoylphor­bol-13-acetate (TPA) showed a small additional activation. A similar weak acti vation was observed for protein kinase from rat brain [1 7]; on the contrary, a marked activation of protein kinase C by TPA was also reported [11] . The difference is probably explained by contaminat ing proteins in the enzyme preparation which might react with TPA or by different reac­t ion conditions. Table I also shows the effect of dibucaine, chlorpromazine, and melittin on protein kinase C. Drugs such as trifluoperazine, chlorpromazine, dibucaine, and melittin have been reported to inhibit both calmodulin-sensitive Ca2

+ ­

dependent protein kinase by interacting with calmodulin and protein kinase C by interacting with membrane phospholipids [18-20]. In our experiments, in the presence of 1 i'g phospha­t idylserine, 500 11M chlorpromazine produced 84 % inhibit ion of protein kinase C, and 500 11M dibucaine or 8 J.LM melittin produced 16% inhibition. In the presence of 0.25 i'g phospha­tidylserine the degree of inhibition was marked, i.e., dibucaine, chlorpromazine, and melittin produced 20%, 93%, and 91 % inhibition, respectively.

c ·a; 0 ..... 0.. C)

2.0

1.5

_§ 1.0 c .E --a> 0 E c

0.5

OL-#------------------------------0,001 0.01 0.1 1.0

Ca2+ CONCENTRATION (mM) FIG 4. Effects of varied calcium concentration on protein kinase C.

The protein kinase C activities were assayed wit h the indicated con­centration of Ca2+ in the presence (e-e) or absence (0-0) of 1 l'g phospholipids, and in t he presence of 200 ng diolein (ll-6).

TABLE I. The activation of protein kinase C

Additions Protein kinase activity (pmol/ min/ mg protein)

Exp. 1

Exp. 2

None" Ca2

+ (100 !J.M) + diolein (200 11gl + TPA (2 ng) + PS,b (1 l'g) + PS + TPA + PS + diolein

None" Ca2+ (100 11M)

+ PS (1 l'g) + PS + dibucaine + PS + chlorpromazine + PS + melittin + PS (0.25 11gl + PS + dibucaine + PS + chlorpromazine + PS + meli ttin

99 116 102 149

2490 2640 2910

47 50

1540 1290 250

1290 1220

976 81

105

Protein kinase C activities were assayed by measuring 32P incorpo­ration into lysine-rich histone during 10-min incubation in the standard reaction mixture (c.f. MateriaL~ and Methods). The concentrations of dibucaine, ch loropromazine, and melittin were 500, 500, and 8 11 M

respectively. • The standard reaction mixture without Ca2+.

bPS = phosphatidylserine.

2 3 4 5

94,000-+-

68,000-+-

43,000-+-

30,000-+-

21,000-+-

6

FIG 5. Autoradiographic analysis of phosphorylated pig epidermal protein. The substrate proteins a re: lanes 1 and 2, protein kinase C (partially purified from pig epidermis); lanes 3 and 4, t he supernatant fraction of pig epidermal homogenate; lon.es 5 and 6, The supernatant fraction plus protein kinase C. The phosphorylation experiments were performed in t he absence (lanes 1, 3, and 5) and presence (lanes 2, 4, an.d 6) of Ca2

+ (100 !J.M) , phosphatidylserine (1 J.Lg), and diolein (200 ng).

264 KOJZUMI ET AL

The results suggest the interaction of these drugs with phos­pholipids to inhibit protein kinase C.

Protein kin ase C of pig epidermis phosphorylated mainly sery l residues of lysine- rich histone. Tyrosyl residues were not phosphorylated (data not shown) .

Phosphorylation of Pig Epidermal Protein by Protein Kinase C

ln order to study phosphorylation of endogenous epidermal protein, t he supernatant fraction of t he epidermal homogenate was incubated with ['y-32P ]ATP and without histone (t he sub­strate in regular enzyme assays). The epidermal protein in the supernatant fraction was phosphorylated by adding Ca2+, phos­phatidylserine, and diolein to the standard reaction mixture. T he data indicate t hat the epidermal homogen ate contains sufficient protein kinase C to phosphorylate t he epidermal protein. When the purified protein kinase C was further added to t he above reaction mixture, t he rate of phosphorylation was increased by 700% (data not shown). In order to detect t he phosp hory lated p rotein the reaction mixture was subjected to SDS-polyacrylamide slab gel electrophoresis fo llowed by pro­te in staining and autoradiography (Fig 5). Polypeptide of97,000 daltons was phosphory lated by adding Ca2+, phosphatidylser­ine, and diolein to the assay mixture. When the protein kinase C fraction from the DE52-column was incubated with Ca2+, phosphatidylseri ne, and diolein wit hout the supernatant frac­tion t he result ing SDS gel analysis showed phosphorylation of some peptides but the 97,000 dalton polypeptide was not phos­phorylated. T his suggests t hat the 97,000 dalton polypeptide is not a phosphorylated for m of protein kinase C itself. The 97,000 dalton polypeptide was not p hosphorylated by the addit ion of Ca2+ alone .

DISCUSSION

The current in vestigation clearly reveals the occurence of protein kinase C in pig epidermis. Since t he protein kinase C activity in the initia l crude homogenate is difficult to assay due to minimal activation with Ca2+ and phosphatidylserine causing a high blank value, we can only estimate an approximate pu ri fication factor in the order of X500; yet the partially puri­fied enzyme is essentially free of cyclic AMP-dependent protein kinase and its subunits. The basal activity of our preparation is low and this a lso suggests t hat the preparation is free of other independent protein kinases. Besides t he obvious differ­ences in cofactor dependency between cyclic AMP-dependent p rotein kinase and protein kinase C, a notable difference is in the substrate proteins (polypeptides) phosphorylated by these two enzymes. Namely with an in vitro phospho rylation system t he former phosphorylates a 45,000, whereas the latter phos­phorylates a 97,000 dalton peptide of pig epidermis. Both of t hem phosphorylate serine residues [21,22) .

Because of the unique activation of protein kinase C by phosphatidylserine and diolein, it has been suggested t hat t his enzyme might be modulated by changes in phospholipid metab­olism by signal transduction at cell membranes. Recently two intriguing papers have been publi shed. One from Nishizuka's laboratory [12) reports t hat the tumor promoter TPA can substitute for diolein in the activation of protein kinase C, and t he other [11] reports solubilization of t he TPA receptor in membrane which subsequent ly can be copurified with protein kinase C. The hypothesis that protein kinase C is identical or shares a pa rt of the TP A receptor is attractive, and one suspects an active role of t his enzyme in growth differentiation and tumor promotion. A specific role of this enzyme in epidermis remains to be investigated. W e are currently studyin g the changes in t he protein kinase C activities and t he characteris­t ics of t he 97,000 dalton substrate peptides in experimental proliferation of epidermis.

Vol. 83, No. 4

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nucleotide-independent protein kinase and its proenzyme in mammalian tissue. I. Purification and characterization of an active enzyme from bovine cerebellum. J Bioi Chern 252:7603-7609, 1977

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11 . Niedel JE, Kuhn LJ, Vanderbark GR: Phorbol diester receptor copuriftes with protein kinase C. Proc Nat\ Acad Sci USA 80:36-40, 1983

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14. Lowry OH, Rosebrough NJ, Farr AL, Randall RJ: Protein meas­urement with Folin phenol reagent. J Bioi Chern 193:265-275, 1951

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17. Le Peuch CJ, Ballester R, Rosen OM: Purified rat brain calcium and phospholipid-dependent protein kinase phosphorylates ri· bosomal protein S6. Proc Natl Acad Sci USA 80:6858- 6862, 1983

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19. Wise BC, Glass DB, Chou CHJ , Raynot RL, Katoh N, Schatzman RC, Turner RS, Kibler RF, Kuo JF: Phospholipid-sensitive Ca2+· dependent protein kinase from heart. II. Substrate specificity and inhibition by various agents. J Bioi Chern 257:8489-8495, 1982

20. Katoh N, Raynor RL, Wise BC, Schatzman RC, Turner RS, Helfman DM, Fain JN, Kuo JF: Inhibition by melittin of phos· pholipid-sensitive Ca2+-dependent protein kinase. Biochem J 202:217-224, 1982

21. lwasa Y, Takai Y, Kikkawa U, Nishizuka Y: Phosphorylation of calf thymus H1 histone by calcium-activated phospholipid-de­pendent protein kinase. Biochem Biophys Res Commun 96:180-187, 1980

22. Yoshikawa K, Takeda J , Nemoto 0 , Ito T, Halprin KM, Adachi K: Phosphorylation of pig epidermal soluble protein by endoge­nous cAMP-dependent protein kinase. J Invest Dermatol 80:108- 111, 1983